| 1. |
- Ali, Safdar, et al.
(författare)
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Electron-ion recombination rate coefficients for C II forming C I
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 753:2, s. 132-
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Tidskriftsartikel (refereegranskat)abstract
- We have determined absolute dielectronic recombination rate coefficients for C II, using the CRYRING heavy-ions storage ring. The resonances due to 2s-2p (∆n = 0) core excitations are detected in the center-of-mass energy range of 0-15 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients are obtained from the DR spectrum by convoluting it with a Maxwell-Boltzmann energy distribution for temperatures in the range of 103-106 K. The derived temperature dependent plasma recombination rate coefficients are presented graphically to compare with the theoretical data available in literature and parameterized by using a fit formula for convenient use in plasma modelling codes. In the temperature range of 103-2×104 K, our experimental results show that previous calculations severely underestimate the plasma rate coefficients and also our AUTOSTRUCTURE calculation does not reproduce the experimental plasma rate coefficients well. Above 2×104 K the agreement between the experimental and theoretical rate coefficients is much better, and the deviations are smaller than the estimated uncertainties.
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| 2. |
- Butorin, S.M, et al.
(författare)
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Tunable excitation x-ray-fluorescence spectroscopy in phase-analysis of high-Tc superconductors
- 1994
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Ingår i: Journal of physics-condensed matter. - 0953-8984. ; 6:43, s. 9267-9274
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Tidskriftsartikel (refereegranskat)abstract
- O Kalpha x-ray fluorescence of YBa2Cu3O7-delta and Sr0.85Nd0.15CuO2 samples containing CO3(2-) impurities, as well as pure BaCO3, have been studied using tunable monochromatic synchrotron radiation excitation. When the excitation energy is set to the most intense features in the O 1s absorption edge of cuprates and to bound states above this edge the O Kalpha spectra recorded are very similar to those of pure BaCO3 even if the admixture of CO3(2-) is small. The observed changes in the O Kalpha profiles of multi-phase YBa2Cu3O7-delta and Sr0.85Nd0.15CuO2 samples are discussed in terms of different x-ray absorption cross sections for O in the main phase and in the CO3(2-) fraction.
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| 3. |
- Böhm, S, et al.
(författare)
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Enhancement of dielectronic recombination by external electromagnetic fields
- 2003
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Ingår i: Hyperfine Interactions. - 0304-3843. ; 146-147:1-4, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- The enhancement of the dielectronic recombination rate of lithiumlike Ne7+ and O5+ ions by external electromagnetic fields has been measured at the storage ring CRYRING. The energy range covered all 1s(2)2pnl dielectronic recombination resonances attached to the 2s --> 2p core excitation. Electric fields up to 1436 V/cm were applied in the Ne7+ experiment and the saturation of the enhancement with increasing electric field could clearly be seen. In the O5+ experiment the enhancement was studied as a function of the Rydberg quantum number n.
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| 4. |
- Böhm, S, et al.
(författare)
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Experimental NV and NeVIII low-temperature dielectronic recombination rate coefficients
- 2005
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Ingår i: Astronomy & Astrophysics. - 0004-6361. ; 437:3, s. 1151-1157
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Tidskriftsartikel (refereegranskat)abstract
- The dielectronic recombination rate coefficients of Nv and Ne viii ions have been measured at a heavy-ion storage ring. The investigated energy ranges covered all dielectronic recombination resonances attached to 2s -> 2p (delta_n = 0) core excitations. The rate coefficients in a plasma are derived and parameterized by using a convenient fit formula. The experimentally derived rate coefficients are compared with theoretical data by Colgan et al. (2004, A&A, 417, 1183) and Nahar & Pradhan (1997, ApJ, 111, 339) as well as with the recommended rate coefficients by Mazzotta et al. (1998, A&A, 133, 403). The data of Colgan et al. and Nahar & Pradhan reproduce the experiment very well over the temperature ranges where Nv and Ne viii are expected to exist in photoionized as well as in collisionally ionized plasmas. In contrast the recommendation of Mazzotta et al. agrees with the experimental rate coefficient only in the collisionally ionized temperature range. At lower temperatures it deviates from the measured rate coefficient by orders of magnitude. In addition the influence of external electric fields with field strengths up to 1300 V/cm on the dielectronic recombination rate coefficient has been investigated.
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| 5. |
- Böhm, S, et al.
(författare)
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Influence of electromagnetic fields on the dielectronic recombination of Ne7+ and O5+ ions
- 2001
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Ingår i: Physica Scripta. Topical Issues. - 0281-1847. ; T92, s. 395-397
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Tidskriftsartikel (refereegranskat)abstract
- Within a series of measurements of the dielectronic recombination (DR) of lithium-like ions we have determined the enhancement of the recombination rate in the presence of crossed electric and magnetic fields for Ne7+ and O5+ ions. In both cases the electron energy range covers a DR resonances attached to 2s --> 2p(1/2) and 2s --> 2p(3/2) Delta_n = 0 core excitations. For increasing field the enhancement factor first increases linearly with the electric field and then saturates. In order to investigate the field effect on high-n Rydberg states the ion energy in the O5+ experiment was changed from 9.4 MeV/u to 5 MeV/u and 3.26 MeV/u. With the variation of the ion energy the field ionization of Rydberg states in the analyzing magnet is influenced. This enabled us to study the field enhancement for a narrow bandwidth of n-states.
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| 6. |
- Böhm, S, et al.
(författare)
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Influence of electromagnetic fields on the dielectronic recombination of Ne7+ ions
- 2001
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 64:3, s. 032707/1-032707/7
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of crossed electric and magnetic fields on dielectronic recombination of Ne7+ ions has been measured at the Stockholm heavy-ion storage ring CRYRING. The electron energy range covered all dielectronic recombination resonances attached to 2s-2p1/2 and 2s-2p3/2 core excitations. Two sets of measurements at magnetic fields of 180 mT and 30 mT have been performed. For the measurement at 180 mT we applied 25 different electric fields between 0 and 1400 V/cm. The resonance strength for dielectronic recombination via high Rydberg states initially increases linearly with electric field and later levels out. At a magnetic field of 30 mT we applied 15 different electric fields ranging from 0 to 140 V/cm. Compared to the measurement at 180 mT the initial slope of the rate enhancement was larger by almost a factor of 2. The fraction of resonant strength not measured due to field ionization is estimated by a model calculation of dielectronic recombination cross sections.
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| 7. |
- Cesar, A, et al.
(författare)
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Resonant x-ray scattering beyond the Born-Oppenheimer approximation: Symmetry breaking in the oxygen resonant x-ray emission spectrum of carbon dioxide
- 1997
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Ingår i: Journal of Chemical Physics. - 0021-9606. ; 106:9, s. 3439-3456
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Tidskriftsartikel (refereegranskat)abstract
- Although resonant x-ray scattering of molecules fulfills strict electronic symmetry selection rules, as now firmly proven by. spectra of diatomic molecules, the accumulated body of data for polyatomic molecules indicates that an apparent breaking of these rules represents the common situation rather than the exception. The CO2 molecule provides a good example of symmetry breaking, with the. oxygen x-ray emission spectra showing strong intensity for transitions that are forbidden by the parity selection rule. We present time-independent and time-dependent theories for frequency-dependent resonant x-ray scattering beyond, the Born-Oppenheimer approximation in order to explore under what circumstances one can anticipate symmetry breaking in the spectra of polyatomic molecules. The theory starts out from the Kramers-Heisenberg dispersion relation and is generalized for vibrational degrees of freedom and for nonadiabatic coupling of the electronic (vibronic) states, including the frequency dependency of, the scattering cross section. Different Limiting cases and few-level models are considered. The symmetry breaking is proven to be the result of pseudo-Jahn-Teller-Like vibronic coupling between near-degenerate core-excited states. Thus vibromic interaction over the antisymmetric vibrational mode between the ''bright'' 1 sigma(g)(-1)2 pi(u)(-1) and ''dark'' 1 sigma(u)(-1)2 pi(u)(-1) intermediate states of CO2 allows transitions otherwise forbidden. The measurements and theory demonstrate that the symmetry-selective character of the resonant x-ray emission is strongly frequency dependent. The strong intensity of ''dipole-forbidden'' transitions in the pi* oxygen K spectrum at resonance is reduced monotonically with the detuning of the excitation energy from resonance, and the spectra become ''symmetry purified.'' Simulations with full vibronic coupling predict this feature of the x-ray scattering experiment and a few-level model explains the energy dependence of the symmetry selection and the symmetry purification at large detuning energies in the limit of narrowband photon excitation.
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| 8. |
- Derevianko, A, et al.
(författare)
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Electric-octupole and pure-electric-quadrupole effects in soft-X-ray photoemission
- 2000
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Ingår i: Physical Review Letters. - 0031-9007. ; 84:10, s. 2116-2119
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Tidskriftsartikel (refereegranskat)abstract
- Second-order [O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms;Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.
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| 9. |
- Dias, E.W.B, et al.
(författare)
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Breakdown of the independent particle approximation in high-energy photoionization
- 1997
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Ingår i: Physical Review Letters. - 0031-9007. ; 78:24, s. 4553-4556
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Tidskriftsartikel (refereegranskat)abstract
- The independent particle approximation is shown to break down for the photoionization of both inner and outer nl (l > 0) electrons of all atoms, at high enough energy, owing to interchannel interactions with the nearby ns photoionization channels. The effect is illustrated for Ne 2p in the 1 keV photon energy range through a comparison of theory and experiment. The implications for x-ray photoelectron spectroscopy of molecules and condensed matter are discussed.
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| 10. |
- Ekengard, Erik, et al.
(författare)
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Antimalarial activity of ruthenium(ii) and osmium(ii) arene complexes with mono- and bidentate chloroquine analogue ligands.
- 2015
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 44:44, s. 19314-19329
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Tidskriftsartikel (refereegranskat)abstract
- Eight new ruthenium and five new osmium p-cymene half-sandwich complexes have been synthesized, characterized and evaluated for antimalarial activity. All complexes contain ligands that are based on a 4-chloroquinoline framework related to the antimalarial drug chloroquine. Ligands are salicylaldimine derivatives, where = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine, and contain non-hydrogen substituents in the 3-position of the salicylaldimine ring, viz. F, Cl, Br, I, NO2, OMe and (t)Bu for , respectively. Ligand is also a salicylaldimine-containing ligand with substitutions in both 3- and 5-positions of the salicylaldimine moiety, i.e. N-(2-((2-hydroxy-3,5-di-tert-butylphenyl)methyl-imino)ethyl)-7-chloroquinolin-4-amine, while is N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) The half sandwich metal complexes that have been investigated are [Ru(η(6)-cym)()Cl] (Ru--Ru-, cym = p-cymene), [Os(η(6)-cym)()Cl] (Os--Os-, Os-, and Os-), [M(η(6)-cym)()Cl2] (M = Ru, Ru-; M = Os, Os-) and [M(η(6)-cym)()Cl]Cl (M = Ru, Ru-; M = Os, Os-). In complexes Ru--Ru- and Ru-, Os--Os-, Os- and Os- and Os-, the ligands were found to coordinate as bidentate N,O- and N,N-chelates, while in complexes Ru- and Os-, monodentate coordination of the ligands through the quinoline nitrogen was established. The antimalarial activity of the new ligands and complexes was evaluated against chloroquine sensitive (NF54 and D10) and chloroquine resistant (Dd2) Plasmodium falciparum malaria parasite strains. Coordination of ruthenium and osmium arene moieties to the ligands resulted in lower antiplasmodial activities relative to the free ligands, but the resistance index is better for the ruthenium complexes compared to chloroquine. Overall, osmium complexes appeared to be less active than the corresponding ruthenium complexes.
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| 11. |
- Eklöw, N, et al.
(författare)
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Magnetic-field dependence in electron-deuteron recombination at very low relative energy
- 2000
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Ingår i: Hyperfine Interactions. - 0304-3843 .- 1572-9540. ; 127:1-4, s. 251-255
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Tidskriftsartikel (refereegranskat)abstract
- The rate coefficient for recombination of D+ with low-energy electrons has been measured at different magnetic fields in the interaction region of the electron cooler at CRYRING. It is found that the measured recombination rate coefficient is influenced by the magnetic field.
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| 12. |
- Fogle, M, et al.
(författare)
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Electron-ion recombination of Be-like C, N, and O
- 2005
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 442:2, s. 757-766
-
Tidskriftsartikel (refereegranskat)abstract
- The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of N3+ and O4+. Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of O4+, the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures.
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| 13. |
- Glans, Isabelle, et al.
(författare)
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Association Between Dietary Habits in Midlife With Dementia Incidence Over a 20-Year Period
- 2023
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Ingår i: Neurology. - : LIPPINCOTT WILLIAMS & WILKINS. - 0028-3878 .- 1526-632X. ; 100:1, s. E28-E37
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Tidskriftsartikel (refereegranskat)abstract
- Background and ObjectivesDementia cases are expected to triple during the next 30 years, highlighting the importance of finding modifiable risk factors for dementia. The aim of this study was to investigate whether adherence to conventional dietary recommendations or to a modified Mediterranean diet are associated with a subsequent lower risk of developing all-cause dementia, Alzheimer disease (AD), vascular dementia (VaD), or with future accumulation of AD-related beta-amyloid (A beta) pathology.MethodsBaseline examination in the prospective Swedish population-based Malmo Diet and Cancer Study took place in 1991-1996 with a follow-up for incident dementia until 2014. Nondemented individuals born 1923-1950 and living in Malmo were invited to participate. Thirty thousand four hundred forty-six were recruited (41% of all eligible). Twenty-eight thousand twenty-five had dietary data and were included in this study. Dietary habits were assessed with a 7-day food diary, detailed food frequency questionnaire, and 1-hour interview. Main outcomes were incident all-cause dementia, AD, or VaD determined by memory clinic physicians. Secondary outcome was A beta-accumulation measured using CSF A beta 42 (n = 738). Cox proportional hazard models were used to examine associations between diet and risk of developing dementia (adjusted for demographics, comorbidities, smoking, physical activity, and alcohol).ResultsSixty-one percent were women, and the mean (SD) age was 58.1 (7.6) years. One thousand nine hundred forty-three (6.9%) were diagnosed with dementia (median follow-up, 19.8 years). Individuals adhering to conventional dietary recommendations did not have lower risk of developing all-cause dementia (hazard ratio [HR] comparing worst with best adherence, 0.93, 95% CI 0.81-1.08), AD (HR 1.03, 0.85-1.23), or VaD (HR 0.93, 0.69-1.26). Neither did adherence to the modified Mediterranean diet lower the risk of developing all-cause dementia (HR 0.93 0.75-1.15), AD (HR 0.90, 0.68-1.19), or VaD (HR 1.00, 0.65-1.55). The results were similar when excluding participants developing dementia within 5 years or those with diabetes. No significant associations were found between diet and abnormal A beta accumulation, conventional recommendations (OR 1.28, 0.74-2.24) or modified Mediterranean diet (OR 0.85, 0.39-1.84).DiscussionIn this 20-year follow-up study, neither adherence to conventional dietary recommendations nor to modified Mediterranean diet were significantly associated with subsequent reduced risk for developing all-cause dementia, AD dementia, VaD, or AD pathology.
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| 14. |
- Glans, Isabelle, et al.
(författare)
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Associations of modifiable and non-modifiable risk factors with cognitive functions - a prospective, population-based, 17 years follow-up study of 3,229 individuals
- 2024
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Ingår i: Alzheimer's Research & Therapy. - : BMC. - 1758-9193. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Although several cardiovascular, demographic, genetic and lifestyle factors have been associated with cognitive function, little is known about what type of cognitive impairment they are associated with. The aim was to examine the associations between different risk factors and future memory and attention/executive functions, and their interaction with APOE genotype. Methods Participants from a large, prospective, population-based, Swedish study were included (n = 3,229). Linear regression models were used to examine baseline hypertension, body mass index (BMI), long-term glucose levels (HbA(1c)), different lipid levels, physical activity, alcohol consumption, smoking, education, APOE genotype, age and sex. All models were adjusted for follow-up time and basic demographics, and, in a second step, all significant predictors were included to examine independent effects. Follow-up outcomes were memory and attention/executive functions. Results The mean age at baseline was 56.1 (SD 5.7) years and 59.7% were women. The mean follow-up time was 17.4 (range 14.3-20.8) years. When examining independent effects, APOE epsilon 4 genotype(p < 0.01), and higher HbA(1c)(p < 0.001), were associated with future low memory function. Higher BMI (p < 0.05), and HbA(1c)(p < 0.05), lower high-density lipoprotein cholesterol (HDL-C)(p < 0.05)and stroke(p < 0.001) were associated with future low attention/executive function. The strongest factors associated with both better memory and attention/executive functions were higher education and alcohol consumption. Further, significant interaction effects between predictors and APOE genotype were found. For memory function, the protective effects of education were greater among epsilon 4-carriers(p < 0.05). For attention/executive function, the protective effects of alcohol were greater among epsilon 2 or epsilon 4-carriers(p < 0.05). Also, attention/executive function was lower among epsilon 4-carriers with higher BMI(p < 0.05) and epsilon 2-carriers with higher HbA1c-levels(p < 0.05). Conclusions Targeting cardiovascular risk factors in mid-life could have greater effect on future attention/executive functions rather than memory, whereas targeting diabetes could be beneficial for multiple cognitive domains. In addition, effects of different risk factors may vary depending on the APOE genotype. The varied cognitive profiles suggest that different mechanisms and brain regions are affected by the individual risk factors. Having detailed knowledge about the specific cognitive effects of different risk factors might be beneficial in preventive health counseling.
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| 15. |
- Glans, Lotta, et al.
(författare)
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Ruthenium(ii) arene complexes with chelating chloroquine analogue ligands: Synthesis, characterization and in vitro antimalarial activity.
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 41:9, s. 2764-2773
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Tidskriftsartikel (refereegranskat)abstract
- Three new ruthenium complexes with bidentate chloroquine analogue ligands, [Ru(η(6)-cym)(L(1))Cl]Cl (1, cym = p-cymene, L(1) = N-(2-((pyridin-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine), [Ru(η(6)-cym)(L(2))Cl]Cl (2, L(2) = N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) and [Ru(η(6)-cym)(L(3))Cl] (3, L(3) = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine) have been synthesized and characterized. In addition, the X-ray crystal structure of 2 is reported. The antimalarial activity of complexes 1-3 and ligands L(1), L(2) and L(3), as well as the compound N-(2-(bis((pyridin-2-yl)methyl)amino)ethyl)-7-chloroquinolin-4-amine (L(4)), against chloroquine sensitive and chloroquine resistant Plasmodium falciparum malaria strains was evaluated. While 1 and 2 are less active than the corresponding ligands, 3 exhibits high antimalarial activity. The chloroquine analogue L(2) also shows good activity against both the chloroquine sensitive and the chloroquine resistant strains. Heme aggregation inhibition activity (HAIA) at an aqueous buffer/n-octanol interface (HAIR(50)) and lipophilicity (D, as measured by water/n-octanol distribution coefficients) have been measured for all ligands and metal complexes. A direct correlation between the D and HAIR(50) properties cannot be made because of the relative structural diversity of the complexes, but it may be noted that these properties are enhanced upon complexation of the inactive ligand L(3) to ruthenium, to give a metal complex (3) with promising antimalarial activity.
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| 16. |
- Glans, Lotta, et al.
(författare)
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Synthesis and biological activity of cymantrene and cyrhetrene 4-aminoquinoline conjugates against malaria, leishmaniasis, and trypanosomiasis.
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 41:21, s. 6443-6450
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Tidskriftsartikel (refereegranskat)abstract
- Organometallic analogues of chloroquine show promise as new antimalarial agents capable of overcoming resistance to the parent drug chloroquine. Here, the synthesis and characterization of three new cymantrene (CpMn(CO)(3)) and cyrhetrene (CpRe(CO)(3)) 4-aminoquinoline conjugates with either an amine or amide linker are reported. The antimalarial activity of the new organometallic conjugates N-(2-(7-chloroquinolin-4-ylamino)ethyl)-4-cymantrenylbutanamide (), N-(2-(7-chloroquinolin-4-ylamino)ethyl)-4-cyrhetrenylbutanamide () and N-(7-chloroquinolin-4-yl)-N'-(cymantrenylmethyl)ethane-1,2-diamine () was evaluated against a chloroquine-sensitive (CQS) and a chloroquine-resistant strain (CQR) of the malaria parasite Plasmodium falciparum. The cymantrene complex with an amine linker () showed good activity against the CQS strain but was inactive against the CQR strain. In contrast, cymantrene and cyrhetrene compounds with an amide linker were active against both the CQS and the CQR strain. In addition, the antibacterial, anti-trypanosomal and anti-leishmanial activity of the compounds was evaluated. Compound showed submicromolar activity against Trypanosoma brucei at a concentration where the toxicity to normal human cells is low. No significant effect was noticed on the exchange of manganese for rhenium in the CpM(CO)(3) moiety in any of the biological assays.
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| 17. |
- Glans, Lotta, et al.
(författare)
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Synthesis, characterization and antimalarial activity of new chromium arene-quinoline half sandwich complexes.
- 2011
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Ingår i: Journal of Inorganic Biochemistry. - : Elsevier BV. - 1873-3344 .- 0162-0134. ; 105:7, s. 985-990
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Tidskriftsartikel (refereegranskat)abstract
- Organometallic analogs of chloroquine (CQ) are of interest as drug candidates that may be able to overcome the widespread chloroquine resistance developed by malaria parasites. Two new chromium arene CQ-analogs: [η(6)-N-(7-chloroquinolin-4-yl)-N'-(2-dimethylamino-methylbenzyl)-ethane-1,2-diamine]tricarbonylchromium 4 and [η(6)-N-(7-chloroquinolin-4-yl)-N'-(2-dimethylaminobenzyl)-ethane-1,2-diamine]tricarbonylchromium 9 have been synthesized and characterized. In addition, X-ray crystal structures of the intermediates (η(6)-benzyldimethylamine)tricarbonylchromium 2, [η(6)-2-((dimethylamino)methyl) benzaldehyde]tricarbonylchromium 3 and p-(η(6)-dimethylaminobenzaldehyde)tricarbonyl chromium 8 are reported. Compound 4 was more active than chloroquine against both CQ-sensitive and CQ-resistant strains of Plasmodium falciparum when antimalarial activity was tested in vitro. The activity of 4 against the CQ-resistant parasite strain was twice as high as for the organic ligand alone (IC(50) values of 33.9nM versus 63.1nM).
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| 18. |
- Glans, Peter, et al.
(författare)
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Determination of the lifetime width of the argon L1-hole state
- 1993
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Ingår i: Physical Review A (Atomic, Molecular, and Optical Physics). - 1050-2947. ; 47:2, s. 1539-1542
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Tidskriftsartikel (refereegranskat)abstract
- The width of the argon 2s level was experimentally obtained from x-ray emission-spectroscopy (2.25+/-0.15 eV) and x-ray photoelectron-spectroscopy (XPS) (2.25+/-0.05 eV) measurements. A theoretical value of 1.85 eV was obtained by a Green's-function calculation. A high-energy satellite located 2.7+/-0.2 eV above the L1-M2,3 x-ray emission transition was confirmed and identified as the 2s(-1)3p-1-->3p-2 double-hole transition. The XPS measurement of the argon 2s ionization energy gave a value of 326.25(5) eV.
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| 19. |
- Glans, Peter, et al.
(författare)
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Dielectronic recombination of Li-like fluorine ions
- 1999
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Ingår i: Nuclear Instruments & Methods in Physics Research, Section B (Beam Interactions with Materials and Atoms). - 0168-583X. ; 154:1-4, s. 97-101
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Tidskriftsartikel (refereegranskat)abstract
- Some recent new developments in dielectronic recombination (DR) measurements at heavy-ion storage rings are presented. A DR spectrum measured at CRYRING in Stockholm of F6+ is used to illustrate a few points regarding this kind of measurements. From the spectrum a transversal temperature of the adiabatically expanded electron beam of 3.0(5) meV is deduced, which is slightly higher than expected.
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| 20. |
- Glans, Peter, et al.
(författare)
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Dielectronic recombination of N4
- 2001
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 649:4, s. 043609/1-043609/11
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Tidskriftsartikel (refereegranskat)abstract
- The dielectronic recombination spectrum of N4+ has been measured with high resolution and accuracy. The 1s22p5l resonances in the energy range from 0 to 1.6 eV were studied in detail. The experimental spectrum is compared with the results from four different calculations. An almost perfect agreement between the experiment and a calculation which combines relativistic many-body perturbation theory and complex rotation is found. The calculation provides accurate spectroscopic data for all fifty 1s22p5l states. The literature value for the 1s22p5s 1P energy level is found to be off by more than 0.1 eV.
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| 21. |
- Glans, Peter, et al.
(författare)
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Dielectronic recombination used as a tool for spectroscopic studies of highly charged ions
- 2004
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Ingår i: Physica scripta. T. - 0281-1847. ; T110, s. 212-215
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Tidskriftsartikel (refereegranskat)abstract
- Systematic studies of electron-ion recombination for Li-like, Na-like, and Cu-like ions have been made during the last few years at the CRYRING facility. The main purpose has been to measure recombination spectra with such high resolution and accuracy that stringent tests of advanced atomic calculations of doubly excited states can be made. From the comparison with theory it is possible to obtain energy positions, as well as radiative and nonradiative decay rates for the doubly excited states. In addition, for heavy, highly charged ions it is possible to deduce radiative corrections for energy splittings with very high accuracy.
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| 22. |
- Glans, Peter, et al.
(författare)
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Experimental and theoretical investigation of the soft x-ray emission spectrum of molecular oxygen
- 1993
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 26:4, s. 663-673
-
Tidskriftsartikel (refereegranskat)abstract
- A high-resolution x-ray emission spectrum of molecular oxygen is presented. Comparisons with ab initio calculations are made regarding relative intensities, energies, and band profiles for the outer valence, 2PI(g), 4PI(u), 2PI(u), 4SIGMA(g)-, 2SIGMA(g)-, levels. The importance of lifetime-vibrational interference is discussed.
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| 23. |
- Glans, Peter, et al.
(författare)
-
Resonant x-ray emission spectroscopy of molecular oxygen
- 1996
-
Ingår i: Physical Review Letters. - : AMER INST PHYSICS. - 0031-9007. ; 76:14, s. 2448-2451
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant soft x-ray emission spectroscopy has been applied to study the issue of symmetry breaking upon core-hole excitation in molecular oxygen. The results provide direct evidence that the inversion symmetry is not broken in the core-excited states. Furthermore, the experiments themselves demonstrate a new experimental technique of broad applicability for studies of electronic structure and excitation dynamics in free atoms and molecules.
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| 24. |
- Glans, Peter, et al.
(författare)
-
Selectively excited x-ray emission spectra of N2
- 1996
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 82:3, s. 193-201
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant and non-resonant X-ray emission spectra of N-2 are presented. The role of the parity selection rule in the case of homonuclear diatomic molecules is discussed thoroughly and illustrated by the X-ray emission spectra. We also discuss how the parity selection rule and the angular anisotropy of the resonant X-ray emission may affect intensities in a fluorescence yield measurement of N-2. Simulated vibrational band profiles calculated using the lifetime-vibrational interference formula are found to be in excellent agreement with the experimental emission bands.
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| 25. |
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| 26. |
- Glans, Peter, et al.
(författare)
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X-ray emission spectroscopy measurements of fluorine substituted methanes
- 1994
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 27:15, s. 3399-3414
-
Tidskriftsartikel (refereegranskat)abstract
- We present the carbon and fluorine x-ray emission spectra of methane and the fluoromethanes (CH4-xFx, x = 0, 1, 2, 3 and 4), measured in high resolution. Relative x-ray emission intensities in dipole velocity and length gauges have been derived from the independent particle approximation using Hartree Fock ground state molecular orbitals. The results of the calculations are compared with the experimental spectra. In the experimental carbon (K-V) emission spectrum of CF4 We observe dipole-forbidden electronic transitions. We suggest that these transitions arise due to vibronic coupling, i.e. intensity is borrowed from the dipole-allowed transitions.
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| 27. |
- Gunnelin, K, et al.
(författare)
-
Assigning x-ray absorption spectra by means of soft-x-ray emission spectroscopy
- 1998
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 57:2, s. 864-872
-
Tidskriftsartikel (refereegranskat)abstract
- The possibility to symmetry assign x-ray absorption spectra using x-ray emission spectroscopy is demonstrated. The oxygen K spectra of CO2 are used to illustrate the possibility to assign core excitations through excitation-energy and angular dependence of resonantly excited x-ray emission spectra. The Rydberg-associated structures just below the ionization threshold in the O K x-ray absorption spectrum are assigned to be mainly due to excitations to orbitals of sigma(g) character. The results, which contradict some previous literature assignments, are supported by quantum-chemical calculations.
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| 28. |
- Gunnelin, K, et al.
(författare)
-
Bond-length-dependent core hole localization observed in simple hydrocarbons
- 1999
-
Ingår i: Physical Review Letters. - 0031-9007. ; 83:7, s. 1315-1318
-
Tidskriftsartikel (refereegranskat)abstract
- Soft x-ray-emission spectroscopy is applied to measure the amount of dynamic symmetry breaking in core-excited acetylene, ethylene, and ethane. Large variations are observed between the molecules and are rationalized in terms of the different C-C bond lengths: Shorter bond lengths give smaller symmetry breaking. The results also indicate that asymmetric modes are important for all the systems studied, in contradiction to previous assumptions in literature.
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| 29. |
- Guo, J.H., et al.
(författare)
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Resonant excitation x-ray-fluorescence from C-60
- 1995
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52, s. 10681-
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray fluorescence of condensed C-60 has been recorded in high resolution using monochromatic synchrotron radiation excitation. Strong intensity modulation of constituent spectral features is observed with varying excitation energy up to 10 eV above threshold. The energy dependence is interpreted as due to resonant inelastic x-ray scattering, leading to symmetry selection rules governing the two-photon process in the fully symmetric molecule.
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| 30. |
- Gwinner, G., et al.
(författare)
-
Influence of magnetic fields on electron-ion recombination at very low energies
- 2000
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 84:21, s. 4822-4825
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative recombination (inverse photoionization) is believed to be well understood since the beginning of quantum mechanics. Still, modern experiments consistently reveal excess recombination rates at very low electron-ion center-of-mass energies. In a detailed study on recombination of F and C ions with magnetically guided electrons we explored the yet unexplained rate enhancement, its dependence on the magnetic field B, the electron density n(e), and the beam temperatures T-perpendicular to and T-parallel to. The excess scales as T-perpendicular to(-1/2) and, surprisingly, as T-parallel to(-1/2), increases strongly with B, and is insensitive to n(e). This puts strong constraints on explanations of the enhancement.
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| 31. |
- Hedling, Erik, et al.
(författare)
-
Film – 1900-talets kulturella form par préference
- 1998
-
Ingår i: Den välsignade tillväxten: Tankelinjer kring ett århundrade av kapitalism, teknik, kultur och vetenskap. - 9127071073
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 32. |
- Hemmers, O, et al.
(författare)
-
Beyond the dipole approximation: angular-distribution effects in valence photoemission
- 1997
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 30:21, s. L727-L733
-
Tidskriftsartikel (refereegranskat)abstract
- Angular distributions of valence photoelectrons showing effects due to highermultipole photon interactions have been measured for the first time. Neon 2s and 2p photoemission exhibits effects beyond the dipole approximation throughout the 250 to 1200 eV photon-energy range studied. The results suggest that any photoemission experiment, on any sample, can be affected at relatively low photon energies, pointing to a general need for caution in interpreting angle-resolved-photoemission measurements.
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| 33. |
- Hemmers, O., et al.
(författare)
-
Dipole and nondipole angular-distribution effects in valence photoemission from neon
- 2002
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 123:2-3, s. 257-264
-
Tidskriftsartikel (refereegranskat)abstract
- Nondipole angular-distribution parameters γ and δ for neon 2s and 2p photoelectrons have been measured and are compared to all available theoretical data. The agreement is very good throughout the 150-1200 eV photon-energy range studied. Furthermore, the neon 2p dipole angular-distribution parameter β and the 2s to 2p cross-section ratio have been measured throughout the same photon-energy range. The agreement between theoretical data and experiment is excellent.
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| 34. |
- Hemmers, O, et al.
(författare)
-
High-resolution electron time-of-flight apparatus for the soft X-ray region
- 1998
-
Ingår i: Review of Scientific Instruments. - 0034-6748. ; 69:11, s. 3809-3817
-
Tidskriftsartikel (refereegranskat)abstract
- A gas-phase time-of-flight (TOF) apparatus, capable of supporting as many as six electron-TOF analyzers viewing the same interaction region, has been developed to measure energy- and angle-resolved electrons with kinetic energies up to 5 keV. Each analyzer includes a newly designed lens system that can retard electrons to about 2% of their initial kinetic energy without significant loss of transmission; the analyzers can thus achieve a resolving power (E/Delta_E) greater than 10(4) over a wide kinetic-energy range. Such high resolving power is comparable to the photon energy resolution of state-of-the-art synchrotron-radiation beamlines in the soft x-ray range, opening the TOF technique to numerous high-resolution applications. In addition, the angular placement of the analyzers, by design, permits detailed studies of nondipolar angular distribution effects in gas-phase photoemission.
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| 35. |
- Hoffknecht, A, et al.
(författare)
-
Recombination of F6+ with free electrons at very low energies
- 1999
-
Ingår i: Physica Scripta. Topical Issues. ; T80B, s. 298-300
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative and dielectronic recombination of F6+ have been studied at the heavy ion storage ring TSR in Heidelberg. For a detailed investigation of rate enhancement effects at very low electron-ion center-of-mass energies experimental parameters such as the magnetic guiding field, the electron density and the adiabatic expansion factor of the electron beam have been varied systematically. Whereas measurements at different electron densities show no influence on the enhancement and while a variation of the expansion factor evokes the predicted behaviour, we see an increase of the enhancement with increasing axial magnetic field between 20 mT and 70 mT.
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| 36. |
- Hutton, R, et al.
(författare)
-
Photon spectroscopy following electron-capture for the collision systems 10 keV/q Kr(q+) + He (q=7,8,9)
- 1993
-
Ingår i: Physica Scripta. - 0031-8949. ; 48:5, s. 569-572
-
Tidskriftsartikel (refereegranskat)abstract
- Spectral studies following electron capture in slow ion-atom collisions are reported for the collision systems Kr(q+) + He (q = 7, 8, 9) at 10 keV/q. The work introduces part of the spectroscopy program which is beginning at the University of Uppsala ECR ion source facility. In particular a search was made for the 3d(10)4p2P-3d(9)4S(2)2D transitions in Cu-like Kr. This multiplet was found to give transitions with wavelengths 198.56, 194.65 and 190.97 angstrom for the 3/2-5/2, 3/2-3/2 and 1/2-3/2 components respectively.
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| 37. |
- LaVilla, R.E., et al.
(författare)
-
Additional features in the 3d-4p x-ray-emission spectrum of Xe
- 1994
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947. ; 49:3, s. 2185-2187
-
Tidskriftsartikel (refereegranskat)abstract
- The high-resolution 3d-4p x-ray-emission spectrum of Xe excited by electron impact was measured. In addition to the prominent peak due to 3d5/2-4p3/2 previously reported, the experimental high-resolution spectrum shows a weak peak, identified as 3d3/2-4P3/2, and satellites. The satellites are tentatively attributed to 3d-1X-1-4p-1X-1 (X = 4s, 4p, and 4d), where the initial doubly ionized states are created by the Auger (Coster-Kronig) decay of the 2p and/or 3p level. The experimental 3d-4p x-ray spectrum is compared with a theoretical spectrum calculated by the ab initio Green's-function method.
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| 38. |
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| 39. |
- Lindroth, Eva, et al.
(författare)
-
QED effects in Cu-like Pb recombination resonances near threshold
- 2001
-
Ingår i: Physical Review Letters. - 0031-9007. ; 86:22, s. 5027-5030
-
Tidskriftsartikel (refereegranskat)abstract
- In an electron-ion recombination study with Pb53+ dielectronic recombination resonances are found for as low as similar to 10(-3)-10(-4) eV relative energy. The resonances have been calculated by relativistic many-body perturbation theory and through comparison with experiment the Pb53+(4p(1/2)-4s(1/2)) energy splitting of similar to 118 eV is determined with an accuracy comparable to the position of the first few resonances, i.e., similar to 10(-3) eV. Such a precision provides a test of QED in a many-body environment at a level which can still not be reached in calculations.
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| 40. |
- Loch, S.D., et al.
(författare)
-
Influence of long-lived metastable levels on the electron-impact single ionization of C2
- 2005
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 71:1, s. 012716-1
-
Tidskriftsartikel (refereegranskat)abstract
- A joint theoretical and experimental investigation is made of the influence of long-lived metastable levels on the electron-impact single ionization of C2+. It is expected that our electron cyclotron resonance ion source produces a beam with 40% of the C2+ ions in the 1s(2)2s(2) S-1(0) ground level and 60% in the 1s(2)2s2p P-3(0,2) excited levels. The comparison of nonperturbative close-coupling calculations with previous single-pass crossed beams and with our multiple-pass storage-ring measurements for the electron-impact ionization of C2+ is consistent with the predicted large metastable fraction. Reasonable agreement is found between the present time-dependent close-coupling, R-matrix with pseudostates, and converged-close-coupling ionization cross-section calculations for the ground and first excited configurations and experimental measurement, assuming a 60% metastable fraction in the ion beam. Distorted-wave calculations are found to overestimate the ionization cross section from both the ground and metastable terms, compared with nonperturbative calculations, resulting in an overestimation of the resultant total cross section when compared with experiment. It is clear that collisional-radiative modeling of the evolution of atomic plasmas through the Be-like ionization stage will need to take into account the role of both ground and metastable levels.
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| 41. |
- Ma, Y, et al.
(författare)
-
Core excitons and vibronic coupling in diamond and graphite
- 1993
-
Ingår i: Physical Review Letters. - 0031-9007. ; 71:22, s. 3725-3728
-
Tidskriftsartikel (refereegranskat)abstract
- The C 1s exciton in diamond is studied by soft x-ray emission excited with high resolution monochromatic photons. A strong phonon sideband of 5 eV wide is observed in the exciton recombination spectrum. With the phonon contribution, the exciton binding energy is estimated to be 1.5 eV. The excited atom is suggested to undergo Jahn-Teller relaxation similar to that of the nitrogen impurities in diamond. A similar exciton is observed at the sigma*-band threshold in graphite. These results provide new insights to the understanding of the core exciton and the donor problem in diamond and other systems.
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| 42. |
- Magnuson, Martin, et al.
(författare)
-
Competition between decay and dissociation of core-excited carbonyl sulfide studied by x-ray scattering
- 1999
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 59:6, s. 4281-4287
-
Tidskriftsartikel (refereegranskat)abstract
- We show evidence of dissociation during resonant inelastic soft x-ray scattering Carbon and oxygen K-shell and sulfur L-shell resonant and nonresonant x-ray emission spectra were measured using monochromatic synchrotron radiation for excitation and ionization. After sulfur L-2,L-3-->pi*, sigma* excitation, atomic lines are observed in the emission spectra as a consequence of competition between de-excitation and dissociation. In contrast thr carbon and oxygen spectra show weaker line-shape variations and no atomic Lines. The spectra are compared to results from ab initio calculations. The discussion of the dissociation paths is based on calculated potential energy surfaces and atomic transition energies.
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| 43. |
- Mahmood, Sultan, et al.
(författare)
-
RECOMBINATION RATE COEFFICIENTS OF BORON-LIKE Ne
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 771:2, s. 78-
-
Tidskriftsartikel (refereegranskat)abstract
- Recombination of Ne5+ was measured in a merged-beam type experiment at the heavy-ion storage ring CRYRING. In the collision energy range 0-110 eV resonances due to 2s(2)2p -> 2s2p(2) (Delta n=0) and 2s(2)2p -> 2s(2)3l (Delta n=1), core excitations were observed. The experimentally derived rate coefficients agree well with the calculations obtained using AUTOSTRUCTURE. At low energies, recombination is dominated by resonances belonging to the spin-forbidden 2s2p(2)(P-4(J))nl series. The energy-dependent rate coefficients were convoluted with a Maxwell-Boltzmann electron energy distribution to obtain plasma recombination rate coefficients. The data from the literature deviate from the measured results at low temperature.
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| 44. |
- Nordgren, J, et al.
(författare)
-
Progress in ultra-soft x-ray emission spectroscopy
- 1991
-
Ingår i: Physica Scripta. Topical Issues. - 0281-1847. ; T34, s. 100-107
-
Tidskriftsartikel (refereegranskat)abstract
- A brief account is given of some recent developments in the use of ultra-soft X-ray emission spectroscopy for studies of electronic structure and excitation dynamics. In particular the novel technique of using monochromatized synchrotron radiation for the excitation of the emission is discussed and some key work presented. Also, photon emission studies in the ultra-soft X-ray range of charge transfer in slow collisions between highly charged ions and atoms are presented.
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| 45. |
- Nordgren, J, et al.
(författare)
-
Resonant soft X-ray fluorescence spectra of molecules
- 1997
-
Ingår i: Applied Physics A (Materials Science Processing). - 0947-8396. ; 65:2, s. 97-105
-
Tidskriftsartikel (refereegranskat)abstract
- A review is presented of some recent advancements in resonant soft X-ray fluorescence spectroscopy applied to molecules. The concept of inelastic scattering is discussed for molecules with an element of symmetry, which introduces degeneracy or near-degeneracy of core excited states. The potential of the symmetry selection rules associated with resonant X-ray fluorescence is illustrated in studies of electronic structure as well as molecular dynamics. The use of polarized photons for exciting X-ray emission is discussed, and examples are presented where anisotropy of X-ray emission provides more detailed information. A brief section discusses the experimental considerations relevant for the spectroscopic technique.
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| 46. |
- Olsen, Martin, 1971-
(författare)
-
Nanomechanics – Quantum Size Effects, Contacts, and Triboelectricity
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanomechanics is different from the mechanics that we experience in everyday life. At the nano-scale, typically defined as 1 to 100 nanometers, some phenomena are of crucial importance, while the same phenomena can be completely neglected on a larger scale. For example, the feet of a gekko are covered by nanocontacts that yield such high adhesion forces that the animal can run up on walls and even on the ceiling. At small enough distances, matter and energy become discrete, and the description of the phenomena occurring at this scale requires quantum mechanics. However, at room temperature the transitions between quantized energy levels may be concealed by the thermal vibrations of the system. As two surfaces approach each other and come into contact, electrostatic forces and van der Waals forces may cause redistribution of matter at the nano level. One effect that may occur upon contact between two surfaces is the triboelectric effect, in which charge is transferred from one surface to the other.This effect can be used to generate electricity in triboelectric nanogenerators (TENGs), where two surfaces are repeatedly brought in and out of contact, and where the charge transfer is turned into electrical energy.This thesis concerns nanomechanics addressing whether quantum mechanics play a role in elastic deformation, as well as various mechanical aspects of nanocontacts including electric charging. The objectives are to contribute to the understanding when quantum effects are of importance at the nanolevel, increase the fundamental understanding of the mechanisms responsible for triboelectric phenomena and apply the triboelectric effect to a wind harvesting device.For more insight into whether quantum effects are of importance in nanomechanics, we use a one dimensional jellium model and the standard beam theory allowing the spring constant of an oscillating nanowire cantilever to be calculated. As the nanowire bends, more electron states fit in its cross section, giving rise to an amplitude dependent resonance frequency of the nanowire oscillations.Furthermore, a model for electric field induced surface diffusion of adatoms was developed. The model takes electrostatic forces and van der Waals forces into account as a voltage is applied between a scanning tunneling microscope tip and a sample. The calculated force on the adatoms at the surface of the sample, which is stemming from the inhomogeneous electric field and the dipole moment of the adatoms, is relatively small, but due to thermal vibrations adatoms diffuse and form mounds at the sample.When bringing two different materials into contact, the difference in triboelectric potentials between the materials results in electric charging. To increase the understanding of triboelectricity, a two-level Schottky model, assuming ion transfer, was developed to describe the temperature dependence of the triboelectric effect for a TENG. The two levels correspond to the binding energy for ions on the two surfaces that are brought into contact, where the difference in binding energy enters the Boltzmanndistribution. The model describes the decreasing triboelectric effect in TENG:s with increasing temperature as described in the literature, and results in a separation energy, which is of the right order of magnitude for physically adsorbed atoms.It was recently demonstrated that TENGs can convert wind energy into electrical energy. Here, a TENG based on a plastic film fluttering between two copper electrodes was constructed. It was found that the frequency of the the fluttering film increases linearly with the wind speed. TENG:s designed in this way generate electricity already at low wind speed, and we therefore expect such TENG:s to be useful both as generators and speed sensors in the future.While quantum mechanics is of importance in a limited number of nanomechanical systems, nanocontacts have a broader meaning, and are crucial for the understanding of triboelectric phenomena. We anticipate that the findings in this thesis will contribute to a better understanding of nanomechanics, in particular the mechanism of triboelectricity.
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| 47. |
- Orban, Istvan, 1980-, et al.
(författare)
-
Determination of the recombination rate coefficients for Na-like Si IV forming Mg-like Si III
- 2006
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 459:1, s. 291-296
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. Absolute, total recombination rate coefficients for Si IV were determined using the CRYRING heavy-ion storage ring. Calculated rate coefficients were used to estimate recombination into states that could not be detected in the experiment because of field ionization. Total, as well as separate, radiative and dielectronic plasma recombination rate coefficients were determined. Methods. Stored ions were merged with an expanded electron beam in the electron cooler section of the storage ring. Recombined ions were separated from the stored ion beam in the first dipole magnet after the electron cooler and were detected with unity efficiency. The absolute radiative and dielectronic recombination rate coefficients were obtained over a center-of-mass energy range of 0-20 eV, covering Δ n = 0 core excitations up to the 3s → 3d series limit. The results of an intermediate coupling AUTOSTRUCTURE calculation were compared with the experiment. The theoretical results were also used to estimate the contribution to dielectronic recombination by high Rydberg states, which were not detected because of field ionization. The spectra were convoluted with Maxwell-Boltzmann energy distributions in the 103-10 6 K temperature range. Results. The resulting plasma recombination rate coefficients are presented and compared with theoretical results frequently used for plasma modeling. In the 103-104 K range, a significant underestimation of the calculated dielectronic recombination plasma rate coefficients was observed. Above 3 × 104 K, the agreement between our dielectronic recombination plasma rate coefficients and two of the previously published rate coefficients is better than 20%. Conclusions. The observed differences between the experimental and calculated recombination rate coefficients at low temperatures reflect the need for benchmarking experiments. Our experimentally-derived rate coefficients can guide the development of better theoretical models and lead to more accurately-calculated rate coefficients.
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| 48. |
- Orban, Istvan, et al.
(författare)
-
Effects of spin-forbidden resonances on the recombination of Be-like Si and Be-like Ne
- 2011
-
Ingår i: Physica Scripta. - : IOP Publishing Ltd. - 0031-8949 .- 1402-4896. ; T144, s. 014035-
-
Tidskriftsartikel (refereegranskat)abstract
- Recombination through doubly excited states that can be formed only through spin-flip of the excited electrons can give very strong contributions to the recombination rate of Be-like ions. We demonstrate this, in this paper, with the electron-ion recombination spectra of Be-like Ne(6+) and Be-like Si(10+), recently measured at the CRYRING storage ring. These resonances have significant effects on the plasma rate coefficients. We show that neglect or imprecise calculation of these resonances is responsible for large spreads observed between various theoretical results from the literature.
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| 49. |
- Orban, Istvan, 1980-, et al.
(författare)
-
Spectroscopic study of doubly excited states in Mg-like Si using dielectronic recombination
- 2007
-
Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 40:5, s. 1063-1080
-
Tidskriftsartikel (refereegranskat)abstract
- We present calculated and experimentally derived electron-ion recombination rate coefficients for Na-like Si IV, recombining into Mg-like Si III, and provide accurate spectroscopic data for doubly excited states located above the ionization threshold of Si III. The experimental recombination rate coefficients were measured in a merged-beam-type experiment at the heavy-ion storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm. Changing the electron-ion relative energy from 0 to 20 eV we covered the energy region from the first to the third ionization threshold. We find that even for the low-charged Si2+ ion, a relativistic many-body perturbation theory calculation is necessary, to describe the recombination rate coefficients in the low-energy region, up to 1.5 eV, satisfactorily. Doubly excited states, forbidden to form in LS coupling, are responsible for the most prominent dielectronic recombination resonances at low energies and contribute with 40% to the strength. Several wide resonances give rise to a plateau-like formation in the recombination spectrum. A broader energy range, up to 6.7 eV, was covered with a non-relativistic many-body calculation. This range contains, in addition to 3pnl resonances, several resonances of the type 3dnl, with the LS-forbidden 3d(2) F-3 states giving rise to a strong, isolated peak at 2.976 eV. The NIST database lists eleven doubly excited states of Si III with energy positions deviating considerably from our determination. Since the listed lines are also not fully matching those with the largest fluorescence yields it must be concluded that they are misidentified.
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| 50. |
- Schuch, R, et al.
(författare)
-
A first study of dielectronic recombination with the super-expanded electron beam in CRYRING
- 1998
-
Ingår i: Hyperfine Interactions. - 0304-3843. ; 115:1-4, s. 123-127
-
Tidskriftsartikel (refereegranskat)abstract
- A first temperature measurement of the expanded electron beam from a super-conducting magnet in the cooler of CRYRING is reported. It is based on detection of a dielectronic recombination resonance in C2+. For this measurement C3+ was stored in the ring at 3 MeV/amu energy. A fit to the resonance with free transverse and longitudinal temperatures gave 3.9 x 10(-3) eV and 4.5 x 10(-5) eV,respectively. The result is also compatible with the values of 10(-3) eV for the transverse and 6.7 x 10(-5) eV for the longitudinal component, in good agreement with expected values.
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