| 1. |
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| 2. |
- Aldenius, Maria
(författare)
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Laboratory wavelengths for cosmological constraints on varying fundamental constants
- 2009
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T134, s. 014008-014008
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Konferensbidrag (refereegranskat)abstract
- Cosmological investigations, using high-redshift quasi-stellar object (QSO) absorption spectra, of possible variations of the fine-structure constant (alpha) require very accurate laboratory wavelengths for a number of resonance transitions from several different species. A change in alpha could be detected as a shift in the wavelengths of atomic transitions in the QSO systems and to accurately determine the values of such shifts it is essential that the laboratory rest wavelengths are known to a high degree of accuracy and precision. The present status of such laboratory wavelengths is discussed with emphasis on our recent study including laboratory wavelengths and wavenumbers of ultraviolet (UV) resonance lines from seven species, measured using the UV high-resolution Fourier transform spectrometer in Lund. The high relative accuracy of the wavenumbers has been obtained by the use of a composite hollow-cathode light source, which enables the spectra of the different species to be recorded simultaneously and thereby minimizes the effects from several steps of calibration. Much emphasis has been put on investigations of possible wavenumber shifts from line structure and self-absorption as well as pressure shifts and calibration effects. The absolute as well as the relative wavenumber accuracy is discussed and the wavenumbers are compared with values from other investigations.
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| 3. |
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| 4. |
- Andersson, Bo, et al.
(författare)
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Implications of a large vector meson production on quark jet fragmentation and large p T reactions
- 1978
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 18:4, s. 193-195
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Tidskriftsartikel (refereegranskat)abstract
- A large vector meson production in quark jet fragmentation implies characteristic differences between the kaon and pion spectra. This prediction is verified in a recent SLAC-MIT experiment. Similar considerations are relevant for the c-quark fragmentation into D-mesons, as observed in ν scattering experiments.The difference in kaon and pion spectra provides a test of the hard quark-quark scattering description of large p T events. In particular the K+/π+ ratio (∼ 1/2 for single particle triggers) should be around 0.1-0.2 for jet triggers.
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| 5. |
- Andersson, Bo, et al.
(författare)
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Quark Jet Fragmentation
- 1979
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 19:2, s. 184-190
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Tidskriftsartikel (refereegranskat)abstract
- A semiclassical model is presented for the way the energy of a fast quark is transformed into observable hadrons. It reproduces the features of 1 + 1 dimensional QED (the Schwinger model) concerning a flat rapidity distribution in the central region. In particular the model predicts that the probability to find a meson containing a leading quark is independent of the Feynman scaling variable. Also a quark jet interpretation of low PT jets in hadronic interactions is discussed shortly.
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| 6. |
- Bardyszewski, Witold, et al.
(författare)
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A New Approach to the Theory of Photoemission from Solids
- 1985
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 32, s. 439-439
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Tidskriftsartikel (refereegranskat)abstract
- By neglecting certain terms in the Hamiltonian (of importance only in the immediate neighbourhood of the threshold energy) we are able to write an exact expression for the photoemission intensity which involves the standard time inverted LEED state and broadened hole-states. If inelastic extrinsic losses are neglected our expression is similar to the one used by e.g. Feibelman and Eastman [1], Pendry [2] and Spanjaard et al. [3]. Our theory also allows inelastic losses (including interference between intrinsic and extrinsic losses) to be evaluated. The expressions are similar to those obtained by Inglesfield [4], but the damping effect no longer has to be put in by hand. Our theory further can handle not only core electron but also valence electron photoemission and it is not restricted to metals but applies to all types of solids. We have also traced why and when Inglesfield's one step theory agrees with a semiclassical calculation.
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| 7. |
- Behringer, Hans, et al.
(författare)
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Dynamics of biomolecular processes PREFACE
- 2013
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 87:5, s. 058501-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Belfrage, Christina, et al.
(författare)
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Doppler-Free Laser Spectroscopy Measurements on a Ne Discharge for Determination of 22Ne-20Ne Isotope Shifts
- 1983
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 27:5, s. 357-370
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Tidskriftsartikel (refereegranskat)abstract
- We have used Doppler-free polarization spectroscopy, intermodulated fluorescence and intermodulated optogalvanic spectroscopy for measuring isotope shifts in 6 Ne lines connecting the 2p53s and 2p53p configurations. The measurements were performed on two different hollow cathodes. For the 5852, 5882, 5945, 5976, 6143 and 6164 A lines the 22Ne-20Ne isotope shift was found to be 2300(15), 1740(2), 1717(3), 1728(5), 1669(4) and 1663(5) MHz, respectively. These results are in fair agreement with previous optical spectroscopy data.
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| 9. |
- Belin, G, et al.
(författare)
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Electronic gJ Factors, Natural Lifetimes, and Electric Quadrupole Interaction for Rb 87 in the np ^(2)P_(3/2) Series of the Rb I Spectrum
- 1971
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 4:6, s. 269-273
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Tidskriftsartikel (refereegranskat)abstract
- For Rb 87 the level crossing method was applied to the first four levels ( n = 5, 6, 7, and 8) of the np 2 P 3/2 series in the Rb I spectrum. By using magnetic dipole interaction constants from corresponding zero field optical double resonance experiments, the electronic g J factors of 5, 6, and 7 p 2 P 3/2 were calculated from the level crossing data. For these levels the natural radiative lifetimes were determined from the half-widths of the level crossing signals. For 8 p 2 P 3/2 the a factor was obtained assuming g J = -1.336 (2). From the measured electric quadrupole interaction constants b , decreasing values of the nuclear quadrupole moment Q were obtained in 5, 6, 7, and 8 p 2 P 3/2 . When core polarization effects are taken into account, the different 2 P 3/2 levels yield consistent values for the quadrupole moment. We find ----- -- g J (5 p 2 P 3/2 ) = -1.3362 (6) -- g J (6 p 2 P 3/2 ) = -1.3347 (10) ----- -- Ï (5 p 2 P 3/2 ) = 25.8 (8) ns -- Ï (6 p 2 P 3/2 ) = 111 (3) ns ----- -- b (5 p 2 P 3/2 ) = 12.510 (57) MHz -- b (6 p 2 P 3/2 ) = 3.947 (13) MHz ----- -- Q (5 p 2 P 3/2 ) = 0.131 barn -- Q (6 p 2 P 3/2 ) = 0.133 barn ----- -- g J (7 p 2 P 3/2 ) = -1.3359 (11) -- a (8 p 2 P 3/2 ) = 6.747 (14) MHz ----- -- Ï (7 p 2 P 3/2 ) = 233 (10) ns -- b (8 p 2 P 3/2 ) = 0.933 (20) MHz ----- -- b (7 p 2 P 3/2 ) = 1.768 (8) MHz -- Q (8 p 2 P 3/2 ) = 0.131 barn ----- -- Q (7 p 2 P 3/2 ) = 0.133 barn -- ----- Considering possible sources of error in the evaluation of the quadrupole moment we obtain Q (Rb 87 ) = +0.132 (9) barn.
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| 10. |
- Belin, G, et al.
(författare)
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Hyperfine Interaction, Zeeman and Stark Effects for Excited States in Potassium
- 1975
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 12:5, s. 287-294
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Tidskriftsartikel (refereegranskat)abstract
- Using the optical double resonance and level crossing methods, properties of several excited S , P , and D states in 39 K were studied. The S and D states were populated using stepwise excitation with the first P state as an intermediate level. An rf lamp and a CW dye laser were used in the first and second excitation steps, respectively. The studied P states were populated in the cascade decay of states, excited with the laser. The following results for the magnetic depole interaction constant a, the Landé g J factor, and the tensor polarizability α 2 were obtained for the studied states: 7 2 S 1/2 : a = 10.78(5) MHz, g J = 2.0020(10); 8 2 S 1/2 : a = 5.99(8) MHz, g J = 2.0028(12); 6 2 P 1/2 : a = 4.05(7) MHz, g J = 0.6663(4); 6 2 P 3/2 : a = 0.89(5) MHz, g J = 1.3337(8); 7 2 P 1/2 : a = 2.18(5) MHz, g J = 0.6659(6); 7 2 P 3/2 : a = 0.49(4) MHz, g J = 1.3336(8); 5 2 D 3/2 : |a| = 0.44(10) MHz, g J = 0.7997(7), |α 2 | = 9.64(45) MHz/(kV)/cm) 2 ; 5 2 D 5/2 : |a| = 0.24(7) MHz, g J = 1.2004(10), |α 2 | = 13.4(7) MHz/(kV)/cm) 2 ; 6 2 D 3/2 : |a| = 0.2(2) MHz, g J = 0.7997(14), |α 2 | = 33.8(1.7) MHz/(kV)/cm) 2 ; 6 2 D 5/2 : |a| = 0.1(1) MHz, g J = 1.2013(20), |α 2 | = 47.6(2.4) MHz/(kV)/cm) 2 . Theoretical values for the magnetic dipole interaction constant have been obtained using a limited many-body perturbation expansion. The Polarization effect, which is due to single excitations from the restricted Hartree-Fock model, is included to all orders, while the true correlation effect is omitted. The results are compared with the experimental values, and the agreement is found to be quite good. For the S and P states the polarization effect is of the order of 10-20%, and it is responsible for roughly half of the deviation of the Hartree-Fock values from experiment. For the D states, on the other hand, the effects are much more drastic. The sign of the a factors has not been measured. The perturbative calculation yields positive values for all 2 D 3/2 states and negative values for all 2 D 5/2 states. The theoretical magnitudes are in agreement with the observed ones.
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| 11. |
- Belin, G, et al.
(författare)
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Hyperfine Interaction, Zeeman and Stark Effects for Excited States in Rubidium
- 1976
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 13:6, s. 351-362
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Tidskriftsartikel (refereegranskat)abstract
- Highly excited P and D states in 87 Rb were examined using a two-step excitation procedure. A conventional rf lamp and a CW dye laser were used for the first and second step, respectively. The following results for the magnetic dipole interaction constant a , the electric quadrupole interaction constant b , the Landé g J factor, and the tensor polarizability α 2 were obtained in level-crossing and optical-double-resonance experiments: 9 2 P 3/2 : a = 4.05(3) MHz, b =0.55(3) MHz, g J = 1.3335(15) 10 2 P 3/2 : a = 2.60(8) MHz, g J = 1.3332(20) 8 2 D 3/2 : a = 2.840(15) MHz, b = 0.17(2) MHz 8 2 D 5/2 : a = -1.20(15) MHz, g J = 1.1998(15) 9 2 D 3/2 : a = 1.900(10) MHz, b = 0.11(3) MHz 9 2 D 5/2 : a = (-)0.80(15) MHz, g J = 1.1995(15), α 2 = 180.3(9.0) MHz/(kV/cm) 2 Many-body calculations of the hyperfine structure of Rb have been performed. The polarization effect is included to all orders, whereas the correlation effect is omitted. The negative a factors for the 2 D 5/2 states, indicating large perturbations, are explained by the polarization contribution. A review of experimental hyperfine interaction constants, Landé g J factors and tensor polarizabilities for rubidium is given together with theoretical values of the a factors. The quadrupole moment for 87 Rb is obtained from the b factors for the 2 P 3/2 and 2 D 3/2 states, using quadrupole parameters from the many-body calculations. The correlation effect is included in a semi-empirical way.
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| 12. |
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| 13. |
- Blom, Anders
(författare)
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Exact solution of the Zeeman effect in single-electron systems
- 2005
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Ingår i: Physica Scripta. - 0031-8949. ; T120, s. 90-98
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Tidskriftsartikel (refereegranskat)abstract
- Contrary to popular belief, the Zeeman effect can be treated exactly in single-electron systems, for arbitrary magnetic field strengths, as long as the term quadratic in the magnetic field can be ignored. These formulas were actually derived already around 1927 by Darwin, using the classical picture of angular momentum, and presented in their proper quantum- mechanical form in 1933 by Bethe, although without any proof. The expressions have since been more or less lost from the literature; instead, the conventional treatment nowadays is to present only the approximations for weak and strong fields, respectively. However, in fusion research and other plasma physics applications, the magnetic fields applied to control the shape and position of the plasma span the entire region from weak to strong fields, and there is a need for a unified treatment. In this paper we present the detailed quantum- mechanical derivation of the exact eigenenergies and eigenstates of hydrogen-like atoms and ions in a static magnetic. eld. Notably, these formulas are not much more complicated than the better-known approximations. Moreover, the derivation allows the value of the electron spin gyromagnetic ratio g(s) to be different from 2. For completeness, we then review the details of dipole transitions between two hydrogenic levels, and calculate the corresponding Zeeman spectrum. The various approximations made in the derivation are also discussed in details.
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| 14. |
- Borge, M. J. G., et al.
(författare)
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Limits on Neutrino-Mixing from the Internal Bremsstrahlung Spectrum of I-125
- 1986
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Ingår i: Physica Scripta. - 1402-4896 .- 0031-8949. ; 34:6A, s. 591-596
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Tidskriftsartikel (refereegranskat)abstract
- The massive antineutrino recently reported by Simpson in an experiment on tritium decay has not been confirmed by experiments on 35S decay. As an independent check, we report here the negative result of a search for the corresponding antiparticle (a massive neutrino) using the decay of 125I. As a by-product, we give accurate data on internal-bremsstrahlung spectra which we have followed over close to four decades in intensity, and we report a new way of measuring its E1/M1 ratio. The experiment provides a new and very accurate value for the 125I-125Te mass difference of 186.1 ± 0.3 keV.
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| 15. |
- Borge, M. J. G., et al.
(författare)
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Study of the Giant Gamow-Teller Resonance in Nuclear Beta-Decay - the Case of Ar-33
- 1987
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Ingår i: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; 36:2, s. 218-223
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Tidskriftsartikel (refereegranskat)abstract
- Delayed proton and gamma emissions following the beta decay of 33Ar have been studied. From the calculated intensity of the feeding to the T = 3/2 analogue state in 33C1, the proton intensities have been put on an absolute scale leading to a proton branching ratio of 38.7 ± 1.0%. A proton branch to the first excited state in 32S at 2230.2 keV (1π = 2+) with an intensity of 0.77 ± 0.10% was obtained from gamma singles and proton-gamma coincidence data. The complete spectroscopic information on 33Ar allows the Gamow-Teller (GT) strength function from the gound state and up to 9.25 MeV excitation energy in 33C1 to be deduced. The total strength observed in this interval is 2.90 in absolute units.
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| 16. |
- Brage, Tomas, et al.
(författare)
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Core polarization effects on oscillator strengths in neutral zinc
- 1992
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Ingår i: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 45:1, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- The effect of core polarization on the oscillator strength for the resonance transition in neutral zinc is investigated using the multiconfiguration Hartree Fock approach. The use of model potentials and corrections to the dipole operator is compared to a method, where the core polarization is represented by including configuration state functions, with one hole in the 3d core subshell in the CI-expansion. The latter, which is labeled explicit CI, gives results in good agreement with experiment. The reason for deviations in earlier calculations is discussed, together with the validity of the comparison of length and velocity forms of oscillator strengths, as a test of accuracy. The dependence of the model potential results on the choice of cut-off radius is investigated.
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| 17. |
- Brage, Tomas, et al.
(författare)
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Experimental and theoretical study of core-excited states of Mg II
- 1991
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Ingår i: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 44:4, s. 336-342
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Tidskriftsartikel (refereegranskat)abstract
- The 2p(5)3s3p, 3p2, 3s4s, 3s3d, and 3s4f core-excited configurations of Mg II have been studied experimentally by beam-foil spectroscopy and theoretically by multiconfiguration Hartree-Fock calculations with Breit-Pauli relativistic corrections. The previously established energy levels belonging to the former four configurations have been reexamined leading to significant corrections of the 3p2 4D and 3s4s 4P levels. Many previously unidentified spectral lines have now been assigned allowing a confident set of energy levels of the nearly degenerate 3p2, 3s4s, and 3s3d configurations to be established. in addition, the higher lying 3s4f states have been studied allowing the assignment of the prominent, but unidentified line at 3480 angstrom to the 3s4f 4G11/2 --> 3s3d 4F9/2 transition, and the establishment of some 3s3d states which primarily decay by autoionization.
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| 18. |
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| 19. |
- Brault, JW, et al.
(författare)
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Structure and line strengths in extreme jK coupling: an experimental and theoretical study in Ni ii
- 1983
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 28:4, s. 475-475
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Tidskriftsartikel (refereegranskat)abstract
- The spectrum emitted from a nickel hollow cathode has been recorded with a Fourier transform spectrometer. Two dense groups of lines just above 18 000 Å have been identified as the transitions 3d8 (3F)5f-3d8 (3F)6g and 3d8 (3F)5g-3d8 (3F)6h in Ni II. The level structure of the configurations involved in these transitions has been studied by fitting the Slater parameters of the energy matrices to the observations. The fitted parameters have been used for calculating the relative line strengths in the transition arrays. Comparisons with the observed intensities show very good agreement.
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| 20. |
- Carlsson, Gillis, et al.
(författare)
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Calculations of nuclear masses at finite angular momenta
- 2006
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Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 130-133
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Tidskriftsartikel (refereegranskat)abstract
- The macroscopic-microscopic method to calculate nuclear masses is extended into the high-spin regime in order to calculate the nuclear binding energy as a function of proton number, neutron number and angular momentum. We describe the method and exemplify it on recent experimental data.
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| 21. |
- Carlsson, J, et al.
(författare)
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Multiconfiguration Hartree-fock Calculations and Time-resolved Laser Spectroscopy Studies of Hyperfine-structure Constants In Sodium
- 1992
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Ingår i: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 46:5, s. 394-398
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Tidskriftsartikel (refereegranskat)abstract
- Hyperfine structure constants for the ground and first excited states of sodium are calculated using a newly written hyperfine structure program, which is part of the MCHF Atomic Structure Package. The calculated hyperfine structure constants are compared with the most reliable values obtained in other theoretical studies and in experiments. Also, a new accurate experimental determination of the 3p P-2(1/2) state hyperfine structure is presented.
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| 22. |
- Clementson, Joel, et al.
(författare)
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Spectroscopy of M-shell x-ray transitions in Zn-like through Co-like W
- 2010
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 81:1, s. 1-015301
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Tidskriftsartikel (refereegranskat)abstract
- The M-shell x-ray emission of highly charged tungsten ions has been investigated at the Livermore electron beam ion trap facility. Using the SuperEBIT electron beam ion trap and a NASA x-ray calorimeter array, transitions connecting to levels of the ground configurations in the 1500–3600 eV spectral range of zinc-like W44+ through cobalt-like W47+ have been measured. The measured spectra are compared with theoretical line positions and emissivities calculated using the FAC code.
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| 23. |
- Curtis, LJ, et al.
(författare)
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Relativistic empirical specification of transition probabilities from measured lifetime and energy level data
- 1997
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Ingår i: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 56:3, s. 240-244
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Tidskriftsartikel (refereegranskat)abstract
- A relativistic extension is made of methods by which intermediate coupling amplitudes are deduced from measured energy levels and combined with measured lifetimes to obtain transition probabilities within a multiplet between two pure configurations. A procedure for incorporating the relativistic j-dependence of the radial transition integral into the empirical data reduction is presented and applied to the isoelectronic formulation of the 2s(2)-2s2p transitions in the Be sequence and the 6s(2)6p(2)-6s(2)6p7s transitions in the Pb sequence.
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| 24. |
- Davies, Melvyn B, et al.
(författare)
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Is our Sun a singleton?
- 2008
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Ingår i: Physica Scripta. - 0031-8949. ; T130
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Tidskriftsartikel (refereegranskat)abstract
- All stars are formed in some form of cluster or association. These environments can have a much higher number density of stars than the field of the galaxy. Such crowded places are hostile environments: a large fraction of initially single stars will undergo close encounters with other stars or exchange into binaries. We describe how such close encounters and exchange encounters will affect the properties of a planetary system around a single star. We define singletons as single stars which have never suffered close encounters with other stars or spent time within a binary system. It may be that planetary systems similar to our own solar system can only survive around singletons. Close encounters or the presence of a stellar companion will perturb the planetary system, leading to strong planet-planet interactions, often leaving planets on tighter and more eccentric orbits. Thus, planetary systems which initially resembled our own solar system may later more closely resemble the observed exoplanetary systems.
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| 25. |
- DiJulio, Douglas, et al.
(författare)
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Shell model based Coulomb excitation gamma-ray intensity calculations in Sn-107
- 2012
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Ingår i: Physica Scripta. - 0031-8949. ; T150
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present recent shell model calculations, based on a realistic nucleon-nucleon interaction, for the light Sn-107,Sn-109 nuclei. By combining the calculations with the semi-classical Coulomb excitation code GOSIA, a set of gamma-ray intensities has been generated. The calculated intensities are compared with the data from recent Coulomb excitation studies in inverse kinematics at the REX-ISOLDE facility with the nucleus Sn-107. The results are discussed in the context of the ordering of the single-particle orbits relative to Sn-100.
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