J/A+A/707/A141 Theoretical investigation of transition data in SI (Li+, 2026)
Theoretical investigation of transition data of astrophysical importance
in neutral sulphur.
Li W., Amarsi A. M., Jonsson P.
<Astron. Astrophys. 707, A141 (2026)>
=2026A&A...707A.141L 2026A&A...707A.141L (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: atomic data - atomic processes
Abstract:
Accurate and comprehensive atomic data are essential for the modelling
of stellar spectra. Uncertainties in the oscillator strengths of
specific lines used for abundance analyses directly translate into
uncertainties in the derived elemental abundances; and incomplete or
biased atomic data sets can impart significant errors in non-local
thermodynamic equilibrium modelling. Theoretical calculations of
atomic data are therefore crucial to supplement the limited
experimental results. In this work, we present extensive atomic data,
including oscillator strengths, transition rates and lifetimes, for
1,730 electric dipole (E1) transitions among 107 levels in neutral
sulphur (SI) by using the multiconfiguration Dirac-Hartree-Fock
(MCDHF) and relativistic configuration interaction (RCI) methods.
These levels belong to the configurations 3p^3np (n=3-7),3p^3nf
(n=4,5), 3s3p^5, 3p^3ns (n=4-7), and 3p^3nd~(n=3-6). The accuracy of
the computed transition rates is assessed by combining the comparison
of the differences in transition rates between the Babushkin and
Coulomb gauges with a cancellation factor analysis. Approximately 16%
of the ab initio results achieved an accuracy classification of A-B,
corresponding to uncertainties within 10%, as defined by the Atomic
Spectra Database of the National Institute of Standards and Technology
(NIST ASD). Applying a fine-tuning technique was found to
significantly improve the accuracy of the results in the Coulomb
gauge, thereby improving the consistency between the Babushkin and
Coulomb gauges; about 24% of the fine-tuned transition data are
assigned to the accuracy classes A-B.
Description:
Table A.1 presents the energy levels and lifetimes from ab initio and
fine-tuning calculations for S I. Energy levels are given relative to the
ground state and compared with NIST ASD data. The lifetimes are given in
Babushkin (B) and Coulomb (C) gauges, respectively.
Table A.2 presents electric dipole transition data for SI. Upper and lower
states, wavelength, and transition data, i.e. weighted oscillator strength,
log(gf), transition probability, A, and the estimated accuracy class, from
both the ab initio and fine-tuning calculations are shown in the table.
Note that the wavelengths are adjusted to match the level energy values
in NIST ASD.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 108 107 Energy levels and lifetimes for SI
tablea2.dat 165 1730 Electric dipole transition data for SI
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- No Sequential number
6- 22 A17 --- Config Configuration
25- 26 A2 --- Term Term labelling
29 I1 --- J Total angular momentum quantum number
32 A1 --- Parity Parity
35- 42 F8.2 cm-1 Eab Energy levels from ab initio calculation (1)
45- 52 F8.2 cm-1 Eft Energy levels from fine-tuning calculation (1)
55- 64 F10.4 cm-1 ENIST ? Energy levels from NIST ASD (1) (2)
67- 75 E9.3 s tauB-ab ? Lifetime in Babushkin gauge from ab initio
78- 86 E9.3 s tauC-ab ? Lifetime in Coulomb gauge from ab initio
89- 97 E9.3 s tauB-ft ? Lifetime in Babushkin gauge from fine-tuning
100-108 E9.3 s tauC-ft ? Lifetime in Coulomb gauge from fine-tuning
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Note (1): Energy levels are given relative to the ground state.
Note (2): The excitation energies for No. 94 and 95 are not available in the
NIST ASD.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Upper Upper state
26 I1 --- Ju Total angular momentum quantum number of
upper state
29 A1 --- Pu Parity of upper state
32- 54 A23 --- Lower Lower state
57 I1 --- Jl Total angular momentum quantum number of
lower state
60 A1 --- Pl Parity of lower state
63- 73 F11.3 0.1nm lambda Wavelength (1)
76- 82 F7.3 --- loggfB-ab Weighted oscillator strength in Babushkin
gauge from ab initio calculation
85- 91 F7.3 --- loggfC-ab Weighted oscillator strength in Coulomb
gauge from ab initio calculation
94-102 E9.3 s-1 AB-ab Transition probability in Babushkin gauge
from ab initio calculation
105-113 E9.3 s-1 AC-ab Transition probability in Coulomb gauge
from ab initio calculation
116 A1 --- AccB-ab Estimated accuracy class of Babushkin gauge
data from ab initio calculation
119 A1 --- AccC-ab Estimated accuracy class of Coulomb gauge
data from ab initio calculation
122-128 F7.3 --- loggfB-ft Weighted oscillator strength in Babushkin
gauge from fine-tuning calculation
131-137 F7.3 --- loggfC-ft Weighted oscillator strength in Coulomb
gauge from fine-tuning calculation
140-148 E9.3 s-1 AB-ft Transition probability in Babushkin gauge
from fine-tuning calculation
151-159 E9.3 s-1 AC-ft Transition probability in Coulomb gauge
from fine-tuning calculation
162 A1 --- AccB-ft Estimated accuracy class of Babushkin gauge
data from fine-tuning calculation
165 A1 --- AccC-ft Estimated accuracy class of Coulomb gauge
data from fine-tuning calculation
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Note (1): The wavelengths are vacuum wavelengths obtained based on the energy
levels in the NIST ASD.
The wavelengths of the transitions associated with No. 94 and 95
(3p3(4S)7p 5P1,2 were calculated using the energy value of
No. 96 (3p3(4S)7p 5P3).
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Acknowledgements:
Wenxian Li, wxli(at)nao.cas.cn
(End) Wenxian Li [NAOC/CAS], Patricia Vannier [CDS] 28-Jan-2026