| 1. |
- Grumer, Jon, et al.
(författare)
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The effect of an external magnetic field on the determination of E1M1 two-photon decay rates in Be-like ions
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 88
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Tidskriftsartikel (refereegranskat)abstract
- In this work we report on ab initio theoretical results for the magnetic-field-induced 2s 2p 3P0 → 2s2 1S0 E1 transition for ions in the beryllium isoelectronic sequence between Z = 5 and 92. It has been proposed that the rate of the E1M1 two-photon transition 2s 2p 3P0 → 2s2 1S0 can be extracted from the lifetime of the 3P0 state in Be-like ions with zero nuclear spin by employing resonant recombination in a storage ring. This experimental approach involves a perturbing external magnetic field. The effect of this field needs to be evaluated in order to properly extract the two-photon rate from the measured decay curves. The magnetic-field-induced transition rates are carefully evaluated, and it is shown that, with a typical storage-ring field strength, it is dominant or of the same order as the E1M1 rate for low- and mid-Z ions. Results for several field strengths and ions are presented, and we also give a simple Z-dependent formula for the rate. We estimate the uncertainties of our model to be within 5% for low- and mid-Z ions and slightly larger for more highly charged ions. Furthermore we evaluate the importance of including both perturber states, 3P1 and 1P1, and it is s
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| 2. |
- Li, Jiguang, et al.
(författare)
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Magnetic-field-dependent angular distributions and linear polarizations of emissions from the 2p53s 3P2 state in Ne-like ions
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 90
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effect of an external magnetic field on the angular distribution and the linear polarization of the 2s22p53s 3Po 2 → 2s22p6 1S0 emission line in Ne-like ions. Since an electric dipole decay channel is opened by the magnetic field and competes with the inherent magnetic quadrupole transition, these properties strongly depend on the magnetic field strength, B. As an example, we discuss in some detail this transition in neonlike magnesium. This is of special interest, since the B-dependent angular distributions and linear polarization degrees are potentially unique diagnostic tools for the magnetic field in different plasmas.
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| 3. |
- Li, Jiguang, et al.
(författare)
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Theoretical investigation of magnetic-field-induced 2p53s 3P0 - 2p6 1S0 transitions in Ne-like ions without nuclear spin
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 88:1
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Tidskriftsartikel (refereegranskat)abstract
- We report theoretical results for magnetic-field-induced 2p53s 3P0,2 − 2p6 1S0 E1 transitions in Ne-like ions with zero nuclear spin (I = 0) between Mg III and Zn XXI as well as in Ne I.We demonstrate that it is important to include both “perturber” states 2p53s 1P1 and 2p53s 3P1 in order to produce reliable transition rates. Furthermore, we investigate the trends of the rates along the isoelectronic sequence of the 2p53s 3P0,2 − 2p6 1S0 transitions and their competition with the 2p53s 3P0 − 2p53s 3P1 M1 and the 2p53s 3P2 − 2p6 1S0 M2 decays. For the 2p53s 3P0 state the magnetic-field-induced transition becomes the dominant decay channel for the light elements even in a relatively weak magnetic field, and it will therefore prove useful in diagnostics of the strength of magnetic fields in different plasmas. The influence of an external magnetic field on the lifetime of the 2p53s 3P2 state is much smaller but still observable for the ions near the neutral end of the sequence. As a special case, the magnetic field effect on the lifetimes of 2p53s 3P0,2 states of neutral 20Ne is discussed. It is found that the lifetimes are drastically reduced by a magnetic field, which may be an underlying reason for the discrepancies in the lifetime of the 2p53s 3P2 state between experiment [14.73(14) s] and theory (17.63 s).
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| 4. |
- Henderson, M, et al.
(författare)
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Lifetimes of the 5d(9)6p levels in HgIII
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 59:5, s. 4068-4070
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements and theoretical calculations for the lifetimes of the 5d(9)6p levels in Hg nr with J = 0,2,3,4. This is an extension of earlier measurements of the lifetimes of the 5d(9)6p levels in Hg III with J = 1, and now provides data for all 12 of the levels. The results also provide an isoelectronic comparison with earlier studies of these levels in Au II of the Pt sequence, and a homologous comparison with earlier studies of the 4d(9)5p levels in Ag II, Cd III, and In IV in the Pd sequence. [S1050-2947(99)10905-3].
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| 5. |
- Andersson, Martin, et al.
(författare)
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Analysis of the competition between forbidden and hyperfine-induced transitions in Ne-like ions
- 2016
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 93:3
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Tidskriftsartikel (refereegranskat)abstract
- In this work we investigate the decay of the |2p53sP03) state in neon-like ions along the isoelectronic sequence ranging from Z=10 to Z=35. In the absence of a nuclear spin, the magnetic dipole transition to |2p53sP13) is the dominating decay channel. However, for isotopes with a nuclear spin, the interaction between the nuclear magnetic dipole moment and the electronic field introduces a mixing of |2p53sP13) and |P11) into the |P03) state, which in turn opens up a competing hyperfine-induced electric dipole decay channel to the ground state. This hyperfine-induced transition channel clearly dominates over the magnetic dipole channel for the neutral end of the isoelectronic sequence, when present. We give values for the rates of both these competing channels and discuss how the introduction of the hyperfine-induced transition channel could have a dramatic influence on the spectrum, not only because it introduces a new line, but also since it can substantially decrease the intensity of the magnetic dipole 2p53sP03→2p53sP13 line and affect the predicted ionization balance in different plasmas.
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| 6. |
- Andersson, M, et al.
(författare)
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Hyperfine-dependent lifetimes in Be-like ions
- 2009
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 79:3
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical investigations of hyperfine quenching of the two metastable levels 1s(2)2s2p P-3(0) and P-3(2) have been performed along the Be-like isoelectronic sequence for ions between Z=6-22. It is shown that the lifetime of the latter level is sensitive to hyperfine quenching in the beginning of the isoelectronic sequence, but the sensitivity decreases towards the high-Z end. It is also shown that the hyperfine dependent branching fraction between the 2s(2) S-1(0)-2s2p P-3(2) and the 2s2p P-3(1)-2s2p P-3(2) transitions can lead to some rather drastic changes in the spectra. Our predicted value of 0.677 s(-1) for the hyperfine-induced 2s(2) S-1(0)-2s2p P-3(0) transition rate for Ti-47(18+) are in disagreement with a recent experimental value of 0.56(3) s(-1). Our calculated values of this quenching are in agreement with other recent calculations all along the sequence.
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| 7. |
- Andersson, M., et al.
(författare)
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Hyperfine-interaction-dependent 4s4p P-3(2) lifetimes in Zn-like ions
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:6
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical studies on hyperfine-interaction-dependent lifetimes of the 4s4p P-3(2) states of Zn-like ions are reported in this paper. A systematic investigation along the isoelectronic sequence shows that the lifetime of the 4s4p P-3(2) level is very sensitive to hyperfine interaction at the beginning of the sequence, but gets less sensitive going to the higher end. The intensity ratio between the 4s(2) S-1(0)-4s4p P-3(2) and the 4s4p P-3(1)-4s4p P-3(2) transitions was also investigated and it is shown that this ratio is very sensitive to hyperfine interaction. In some isotopes the two branches are dominated by transitions from different upper hyperfine levels. Our research also reveals that the hyperfine-induced electric dipole transitions contribute to the transitions of 4s(2) S-1(0)-4s4p P-3(2) at about the same level as, or even higher than, M2 transitions whenever the nucleus has a spin. This is true all along the isoelectronic sequence.
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| 8. |
- Andersson, M., et al.
(författare)
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Hyperfine-state-dependent lifetimes along the Ni-like isoelectronic sequence
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:4, s. 12-042509
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the lifetime of the 3d(9)4s D-3(3) level along a part of the nickel-like isoelectronic sequence has been performed. The focus of this work has been to evaluate the importance of the hyperfine induced electric quadrupole channel of the 3d(10) S-1(0)-3d(9)4s D-3(3) transition for isotopes with nuclear spin. Comparisons between the magnetic octupole transition rate and the hyperfine-induced electric quadrupole transition rate shows that the hyperfine quenching is of importance along the whole isoelectronic sequence. At the low-Z end the hyperfine induced electric quadrupole transition channel dominates, being several orders of magnitude larger than the rate for the magnetic octupole transition channel, while for higher Z the two rates are of comparable size.
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| 9. |
- Beideck, DJ, et al.
(författare)
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Lifetimes of 5d96p and 5d86s6p levels in Hg iii
- 1993
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 47:2, s. 884-889
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Tidskriftsartikel (refereegranskat)abstract
- Experimental and theoretical studies of lifetimes and transition probabilities for doubly ionized mercury, Hg III, are reported. Such data are currently of great astrophysical interest because observations with the Goddard high resolution spectrograph on board the Hubble space telescope have shown some 5d(9)6s-5d(9)6p transitions of Hg III in the spectrum of the chemically peculiar star chi Lupi. We now report experimental lifetimes for some selected 5d(9)6p and 5d(8)6s6p levels, determined by beam-foil spectroscopy, and compare the results with theoretical transition probabilities based on relativistic multiconfiguration Dirac-Fock calculations.
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| 10. |
- Brage, Tomas, et al.
(författare)
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Effects of Core-valence and Core-core Correlation On the Line-strength of the Resonance Lines In Li-i and Na-i
- 1994
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 49:3, s. 2181-2184
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Tidskriftsartikel (refereegranskat)abstract
- The resonance lines in Li I and Na I both exhibit a puzzling discrepancy between experiment and accurate ab initio calculations. Only results from a semiempirical method, that in principal neglects core-core correlation, agree with the experiments. The agreement with a multiconfiguration Hartree-Fock calculation, including only core-valence correlation, shows that this might be fortuitous. A method for including some core-core correlation is designed and gives results in excellent agreement with other accurate ab initio methods.
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