| 1. |
- Falcinelli, Stefano, et al.
(författare)
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The Fragmentation Dynamics of Simple Organic Molecules of Astrochemical Interest Interacting with VUV Photons
- 2019
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Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:9, s. 1862-1872
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation on the fragmentation dynamics following the double photoionization of simple organic molecules of astrochemical interest, propylene oxide and N-methylformamide molecules, induced by VUV photons has been reported. Experiments used linearly polarized light in the 18–37 eV (propylene oxide) and 26–45 eV (N-methylformamide) photon energy range at the ELETTRA Synchrotron Facility of Trieste (Italy), coupling ion imaging and electron–ion–ion coincidence techniques with time-of-flight mass spectrometry. In the case of propylene oxide, six different two-body fragmentation processes have been recorded with the formation of CH2+/C2H4O+, CH3+/C2H3O+, O+/C3H6+, OH+/C3H5+, C2H3+/CH3O+, C2H4+/CH2O+ ion pairs. On the other hand, the double photoionization of N-methylformamide occurs producing two main fragmentation reactions, forming CH3+ + CH2NO+ and H+ + C2H4NO+. The relative cross sections and the threshold energies for all fragmentation channels are recorded as a function of the photon energy. Furthermore, in the case of the double photoionization of propylene oxide, the measure of the kinetic energy released distribution for the CH3+/C2H3O+ final ions with their angular distributions allowed the identification of a bimodal behavior indicating the possible formation of two different stable isomers of C2H3O+: acetyl and oxiranyl cations. The obtained results are important to clarify the physical chemistry of the elementary processes induced by the interaction of ionizing radiations with simple organic molecules of astrochemical interest: propylene oxide and N-methylformamide.
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| 2. |
- Salén, Peter, et al.
(författare)
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Electronic state influence on selective bond breaking of core-excited nitrosyl chloride (ClNO)
- 2022
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 157:12
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Tidskriftsartikel (refereegranskat)abstract
- The potential for selective bond breaking of a small molecule was investigated with electron spectroscopy and electron-ion coincidence experiments on ClNO. The electron spectra were measured upon direct valence photoionization and resonant core excitation at the N 1s- and O 1s-edges, followed by the emission of resonant-Auger (RA) electrons. The RA spectra were analyzed with particular emphasis on the assignment of the participator and spectator states. The states are of special relevance for investigating how distinct electronic configurations influence selective bond breaking. The electron-ion coincidence measurements provided branching fractions of the produced ion fragments as a function of electron binding energy. They explicitly demonstrate how the final electronic states created after photoionization and RA decay influence fragmentation. In particular, we observed a significantly different branching fraction for spectator states compared with participator states. In addition, it was also observed that the bonds broken for the spectator states correlate with the antibonding nature of the spectator-electron orbital.
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| 3. |
- Schio, Luca, et al.
(författare)
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NEXAFS and XPS studies of nitrosyl chloride
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:14, s. 9040-9048
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of nitrosyl chloride (ClNO) has been investigated in the gas phase by X-ray Photoelectron (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the Cl 2p, Cl 2s, N 1s and O 1s edges in a combined experimental and theoretical study. The theoretical calculations at different levels of approximation predict ionization potential values in good agreement with the experimental data and allow us to assign the main features of the absorption spectra. An unexpected failure of the density functional model is, however, observed in the calculation of the Cl 2s binding energy, which is related to a large self-interaction error. Largely different photoabsorption cross-section patterns are experimentally observed in core excitations from the investigated quantum shells (n = 1, 2). This finding is confirmed by the oscillator strength distributions calculated at different absorption edges; in the case of the n = 2 shell the bands below the threshold are extremely weak and most of the absorption intensity is due to excitations in the continuum.
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| 4. |
- Schio, Luca, et al.
(författare)
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NEXAFS and XPS studies of nitrosyl chloride
- 2015
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Ingår i: Physical Chemistry Chemical Physics - PCCP. - 1463-9076. ; 17:14, s. 9040-9048
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of nitrosyl chloride (ClNO) has been investigated in the gas phase by X-ray Photoelectron (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the Cl 2p, Cl 2s, N 1s and O 1s edges in a combined experimental and theoretical study. The theoretical calculations at different levels of approximation predict ionization potential values in good agreement with the experimental data and allow us to assign the main features of the absorption spectra. An unexpected failure of the density functional model is, however, observed in the calculation of the Cl 2s binding energy, which is related to a large self-interaction error. Largely different photoabsorption cross-section patterns are experimentally observed in core excitations from the investigated quantum shells (n = 1, 2). This finding is confirmed by the oscillator strength distributions calculated at different absorption edges; in the case of the n = 2 shell the bands below the threshold are extremely weak and most of the absorption intensity is due to excitations in the continuum.
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| 5. |
- Alagia, Michele, et al.
(författare)
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Core-shell photoabsorption and photoelectron spectra of gas-phase pentacene : Experiment and theory
- 2005
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Ingår i: Journal of chemical physics Online. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 122:12, s. 124305-
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Tidskriftsartikel (refereegranskat)abstract
- The C K-edge photoabsorption and 1s core-level photoemission of pentacene (C22H14) free molecules are experimentally measured, and calculated by self-consistent-field and static-exchange approximation ab initio methods. Six nonequivalent C atoms present in the molecule contribute to the C 1s photoemission spectrum. The complex near-edge structures of the carbon K-edge absorption spectrum present two main groups of discrete transitions between 283 and 288 eV photon energy, due to absorption to * virtual orbitals, and broader structures at higher energy, involving * virtual orbitals. The sharp absorption structures to the * empty orbitals lay well below the thresholds for the C 1s ionizations, caused by strong excitonic and localization effects. We can definitely explain the C K-edge absorption spectrum as due to both final (virtual) and initial (core) orbital effects, mainly involving excitations to the two lowest-unoccupied molecular orbitals of * symmetry, from the six chemically shifted C 1s core orbitals. ©2005 American Institute of Physics
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| 6. |
- Andersson, Åke, et al.
(författare)
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Single-photon hot-electron ionization of C70
- 2023
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Ingår i: Physical Review A. - 2469-9926 .- 2469-9934. ; 107:1
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Tidskriftsartikel (refereegranskat)abstract
- Gas phase C70 molecules have been ionized with single photons of energies between 16 and 70 eV, and the electron spectra measured with velocity map imaging in coincidence with the ions. The doubly ionized and unfragmented species was present at photon energies of 22 eV and up, and triply charged ions were present from 55 eV. The low-kinetic-energy parts of the spectra are explained with thermal emission of transient hot electrons. We propose a generally applicable mechanism, named resonance ionization shadowing, for the creation of hot electrons by absorption of above-threshold energy photons.
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| 7. |
- Gorczyca, Thomas, et al.
(författare)
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Radiative and Relativistic Effects in the Decay of Highly Excited States in Helium
- 2000
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 85:6, s. 1202-1205
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Tidskriftsartikel (refereegranskat)abstract
- A recent experimental study [J.-E. Rubensson et al., Phys. Rev. Lett. 83, 947 (1999)] measured a significant fluorescence yield of the He( 2lnl′) photoexcited resonances, showing major qualitative differences from nonrelativistic predictions. We present a further theoretical study of these states, and perform R-matrix multichannel quantum defect theory calculations to extract fluorescence and ionization cross sections. These theoretical results are in excellent agreement with newer, higher-resolution measurements. Radiative and spin-orbit effects are quantified and shown to play an important role in the overall characterization of highly excited states.
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| 8. |
- Hansen, Klavs, 1958, et al.
(författare)
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Single Photon Thermal Ionization of C60
- 2017
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 118
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Tidskriftsartikel (refereegranskat)abstract
- We report on experiments which show that C60 can ionize in an indirect, quasithermal boiloff process after absorption of a single photon. The process involves a large number of incoherently excited valence electrons and yields electron spectra with a Boltzmann distribution with temperatures exceeding 104 K. It is expected to be present for other molecules and clusters with a comparatively large number of valence electrons. The astrophysical consequences are briefly discussed.
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| 9. |
- Kassebaum, Nicholas J., et al.
(författare)
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Global, regional, and national disability-adjusted life-years (DALYs) for 315 diseases and injuries and healthy life expectancy (HALE), 1990-2015 : a systematic analysis for the Global Burden of Disease Study 2015
- 2016
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 388:10053, s. 1603-1658
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Tidskriftsartikel (refereegranskat)abstract
- Background Healthy life expectancy (HALE) and disability-adjusted life-years (DALYs) provide summary measures of health across geographies and time that can inform assessments of epidemiological patterns and health system performance, help to prioritise investments in research and development, and monitor progress toward the Sustainable Development Goals (SDGs). We aimed to provide updated HALE and DALYs for geographies worldwide and evaluate how disease burden changes with development. Methods We used results from the Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) for all-cause mortality, cause-specific mortality, and non-fatal disease burden to derive HALE and DALYs by sex for 195 countries and territories from 1990 to 2015. We calculated DALYs by summing years of life lost (YLLs) and years of life lived with disability (YLDs) for each geography, age group, sex, and year. We estimated HALE using the Sullivan method, which draws from age-specific death rates and YLDs per capita. We then assessed how observed levels of DALYs and HALE differed from expected trends calculated with the Socio-demographic Index (SDI), a composite indicator constructed from measures of income per capita, average years of schooling, and total fertility rate. Findings Total global DALYs remained largely unchanged from 1990 to 2015, with decreases in communicable, neonatal, maternal, and nutritional (Group 1) disease DALYs off set by increased DALYs due to non-communicable diseases (NCDs). Much of this epidemiological transition was caused by changes in population growth and ageing, but it was accelerated by widespread improvements in SDI that also correlated strongly with the increasing importance of NCDs. Both total DALYs and age-standardised DALY rates due to most Group 1 causes significantly decreased by 2015, and although total burden climbed for the majority of NCDs, age-standardised DALY rates due to NCDs declined. Nonetheless, age-standardised DALY rates due to several high-burden NCDs (including osteoarthritis, drug use disorders, depression, diabetes, congenital birth defects, and skin, oral, and sense organ diseases) either increased or remained unchanged, leading to increases in their relative ranking in many geographies. From 2005 to 2015, HALE at birth increased by an average of 2.9 years (95% uncertainty interval 2.9-3.0) for men and 3.5 years (3.4-3.7) for women, while HALE at age 65 years improved by 0.85 years (0.78-0.92) and 1.2 years (1.1-1.3), respectively. Rising SDI was associated with consistently higher HALE and a somewhat smaller proportion of life spent with functional health loss; however, rising SDI was related to increases in total disability. Many countries and territories in central America and eastern sub-Saharan Africa had increasingly lower rates of disease burden than expected given their SDI. At the same time, a subset of geographies recorded a growing gap between observed and expected levels of DALYs, a trend driven mainly by rising burden due to war, interpersonal violence, and various NCDs. Interpretation Health is improving globally, but this means more populations are spending more time with functional health loss, an absolute expansion of morbidity. The proportion of life spent in ill health decreases somewhat with increasing SDI, a relative compression of morbidity, which supports continued efforts to elevate personal income, improve education, and limit fertility. Our analysis of DALYs and HALE and their relationship to SDI represents a robust framework on which to benchmark geography-specific health performance and SDG progress. Country-specific drivers of disease burden, particularly for causes with higher-than-expected DALYs, should inform financial and research investments, prevention efforts, health policies, and health system improvement initiatives for all countries along the development continuum.
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| 10. |
- Li, Cui, et al.
(författare)
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Experimental and theoretical XPS and NEXAFS studies of N-methylacetamide and N-methyltrifluoroacetamide
- 2016
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 18:3, s. 2210-2218
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Tidskriftsartikel (refereegranskat)abstract
- Experimental Near-Edge X-ray Absorption Fine-Structure (NEXAFS) spectra of N-methyltrifluoroacetamide (FNMA), which is a peptide model system, measured at the C, N, O and F K-edges are reported. The features in the spectra have been assigned by Static-Exchange (STEX) calculations. Using the same method, we have also assigned previously measured NEXAFS spectra of another peptide model system, N-methylacetamide (NMA). To facilitate the NEXAFS feature assignments, X-ray Photoelectron Spectroscopy (XPS) measurements for NMA and FNMA have been carried out with the aim of obtaining the 1s electron ionization potentials, which are compared with the values predicted by our Hartree-Fock (Delta HF) and Multi Configuration Self Consistent Field (Delta MCSCF) calculations. We also demonstrate an approach to compensate for screening effects that are neglected in the STEX method. Ion yield measurements of FNMA associated with the excitation of several C, N, O, and F K-shell pre-edge resonances have revealed site-specific fragmentation in some cases which we interpret with the aid of our theoretical calculations.
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