| 1. |
- Berzinsh, U, et al.
(författare)
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Radiative lifetimes for the 4p excited states of phosphorus and the oscillator strengths of solar lines
- 1997
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Ingår i: Astronomy & Astrophysics. - 0004-6361. ; 326:1, s. 412-416
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes for the levels of the 3s(2)3p(2)4p configuration in neutral phosphorus have been determined experimentally for the first time and also theoretically. Experiments were performed by using two-photon UV laser excitation and subsequent fluorescence detection in a laser-produced plasma. In relativistic Hartree-Fock calculations, the Cowan code extended to 42 configurations was used. Finally, the lifetimes for all the 13 excited states in the 4p configuration were calculated and for 6 of them the values were measured experimentally. Theoretical branching ratios were combined with experimental lifetimes, to deduce oscillator strengths and these were used for the evaluation of the phosphorus abundance in the sun. A value of 5.49 (0.04) was obtained in the usual logarithmic scale.
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| 2. |
- Biemont, E, et al.
(författare)
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Lifetimes and oscillator strengths for ultraviolet transitions in neutral sulfur
- 1998
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 502:2, s. 1010-1014
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Tidskriftsartikel (refereegranskat)abstract
- A consistent set of f-values for vacuum ultraviolet lines of S I is deduced from a combination of laser lifetime measurements and theoretical branching ratios. The new results are compared with results deduced from absorption by interstellar gas toward zeta Ophiuchi, and good agreement is observed for most transitions.
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| 3. |
- Biemont, E, et al.
(författare)
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Radiative lifetimes, branching fractions and transition probabilities in Ge I - solar implications
- 1999
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 303:4, s. 721-726
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Tidskriftsartikel (refereegranskat)abstract
- New radiative lifetimes have been measured for the 5s (3)P(0,1,2)degrees and 5s (1)P(1)degrees levels of Ge I using a laser-produced plasma subject to selective laser excitation. A diffraction grating based emission spectrometer of moderately high resolution has been used to remeasure the branching ratios of the 4p-5s depopulating transitions. The oscillator strengths of astrophysical interest, which have been derived from these new data, are compared with theoretical values calculated within a pseudo-relativistic Hartree-Fock approach. The new set of f-values has been compared with the few results available in the literature, which are generally characterized by a large scatter and a low accuracy. The solar photospheric abundance of germanium deduced from the new atomic data of the present work is A(Ge) = 3.58 +/- 0.05, on the usual logarithmic scale, in agreement with the meteoritic value.
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| 4. |
- Li, Z. S, et al.
(författare)
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Determination of radiative lifetimes of neutral sulphur by time-resolved three-photon VUV laser spectroscopy
- 1998
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 2:1, s. 11-14
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of the highly exited states 3p(3)8s S-3(1)0 and 3p(3)6d D-3(1,2,3)0 of neutral sulphur have been measured using time-resolved laser-induced fluorescence. The sulphur atoms were generated in a laser-produced plasma. The investigated states were populated through a two-step process involving a two-photon excitation to the lowest excited tripler state of even parity 3p(4) P-3(0,1,2), followed by a one-photon excitation to the investigated state. We obtained tau(8s(3)S(1)(0)) = 40 +/- 5 ns and tau(6d(3)D(1,2,3)(0)) = 75 +/- 7 ns. These values are much longer than theoretically predicted ones and much shorter than those indirectely inferred from astronomical data.
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| 5. |
- Li, Z. S, et al.
(författare)
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Lifetime measurements in odd-parity Rydberg series of neutral lead by time-resolved laser spectroscopy
- 1998
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 57:5, s. 3443-3449
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Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes have been measured in the odd-parity Rydberg series 6pns (n=7-13) and 6pnd (n=6-13) of neutral lead using time-resolved UV laser-induced fluorescence from a laser-produced plasma. A relativistic Hartree-Fock calculation taking configuration interaction into account in a detailed way has also been performed for odd-as well as even-parity states for testing the ability of this approach to correctly predict radiative properties of heavy atoms. A generally good overall agreement between experimental and theoretical lifetimes has been achieved except for a few levels.
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| 6. |
- Li, Z. S, et al.
(författare)
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Lifetime measurements in Yb II with time-resolved laser spectroscopy
- 1999
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 32:7, s. 1731-1737
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Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes of 10 levels of singly ionized ytterbium have been measured with time-resolved laser spectroscopy. Free Yb+ ions were produced in a laser-induced plasma. A stimulated Brillouin scattering technique has been used to produce laser pulses as short as 1 ns for the excitation of short-lived Yb+ states. Pseudo-relativistic Hartree-Fock calculations, taking into account the core-polarization effects, have also been performed. A good agreement of the measured and the calculated lifetime values has been achieved.
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| 7. |
- Li, Z. S, et al.
(författare)
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Radiative properties of neutral germanium obtained from excited-state lifetime and branching-ratio measurements and comparison with theoretical calculations
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:1, s. 198-208
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Tidskriftsartikel (refereegranskat)abstract
- Using time-resolved UV laser-induced fluorescence from a laser-produced plasma, natural radiative lifetimes have been measured for 21 levels of Ge I belonging to the odd-parity 4p4d, 4p5d, and 4p6s configurations. Stimulated Brillouin scattering in water has allowed us to compress Nd:YAG laser pulses pumping a dye laser (where YAG denotes yttrium aluminum garnet), thus yielding 1-ns tunable laser pulses to enable accurate measurements of short lifetimes. Branching ratios of Ge I have been measured by inductively coupled plasma emission spectrometry, the intensity calibration being performed by means of Ar lines emitted by a hollow-cathode lamp. The experimental lifetimes and branching ratios have been combined in order to provide a set of accurate transition probabilities for the 4p-5s and 4p-4d transitions. A relativistic Hartree-Fock; calculation, taking configuration-interaction and polarization effects into account, has been combined with a least-squares optimization procedure of the Slater and spin-orbit integrals in order to test the ability of this approach to correctly predict radiative properties of the group-IV elements. Good agreement between experimental and theoretical transition probability values has been achieved for most of the transitions considered.
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