Lifetime Measurements in Si II, Si III, and Si IV

Berry, H. G.; Bromander, J.; Curtis, L. J.; Buchta, R.

doi:10.1088/0031-8949/3/3-4/007

Cited by 85 publications

(37 citation statements)

References 31 publications

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“…The lifetimes can be measured in general with less uncertainty [10] and Hjorth-Jensen and Aashmar [14], but is lower than the measured value by Berry et al [8]. The lifetime of the a 2 D e state of the present work is within the spread of various measured values and agrees closely only with the value calculated by Mendoza et al [10].…”

Section: Resultssupporting

confidence: 82%

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OSCILLATOR STRENGTHS FOR DIPOLE-ALLOWED FINE-STRUCTURE TRANSITIONS IN Si II

Nahar

1998

Atomic Data and Nuclear Data Tables

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An extensive dataset of oscillator strengths, line strengths, and Einstein A -coefficients has been calculated for a large number of dipole-allowed (ΔS=0) fine-structure transitions in Si II. The line strengths in LS coupling are obtained in an ab initio manner in the close-coupling approximation employing the R-matrix method. The fine-structure components are obtained through algebraic transformations of the LS multiplets. Observed spectroscopic energies are employed whenever available. A 12-state eigenfunction expansion of the core ion, Si III, is employed for the present calculations. This work presents the oscillator strengths of 1122 fine-structure transitions in Si II corresponding to 390 LS multiplets and provides a reasonably complete set of radiative transitions for this astrophysically important ion for the first time. Present results are of comparable accuracy to previous detailed calculations obtained for a small number of transitions and are in reasonably good agreement with the measured oscillator strengths and lifetimes. INTRODUCTIONSi II is one of the most common ions observed in absorption and emission spectra from astrophysical sources, such as the interstellar medium, quasars, hot stars, and the sun. The oscillator strengths for transitions in Si II are used in the determination of abundances, temperatures, densities, and column densities (see, e.g., Ref.[1]). Si II has been investigated both experimentally [2][3][4][5][6][7][8][9] and theoretically [10][11][12][13][14][15][16][17] by many workers. However, all these studies have remained confined to a limited number of transitions until the work of the Opacity Project (OP) [10]. One of the aims of the OP [18] has been to obtain accurate atomic radiative data in an ab initio manner in the close-coupling (CC) approximation using the R-matrix method. The radiative work of the OP was carried out in LS coupling; however, the laboratory plasma experiments and the various astrophysical models usually consider the fine-structure transitions (see, e.g., [2][3][4][5]). The extended non-LTE (low temperature equilibrium) models which consider a number of transitions, such as ones observed in hot stars, require both radiative and collisional data for a large number of energy levels. Collisional data are now available for Si II [19] obtained in the close-coupling approximation using the R-matrix method. The aim of this work is to present an extensive set of radiative data of reliable accuracy for fine-structure transitions in Si II to be used in collisional-radiative models employed in astrophysical applications. Similar sets of data for fine-structure transitions in other ions employing the present method have been reported earlier [20]. Summary of the Theoretical Work and ComputationsThe calculations of the oscillator strengths (f-values), line strengths (S-values), and Einstein coefficients or transition probabilities (A-values) have been described in previous works [20] and are not discussed in detail here. We present only the computational details pe...

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Section: Resultssupporting

confidence: 82%

“…[1]). Si II has been investigated both experimentally [2][3][4][5][6][7][8][9] and theoretically [10][11][12][13][14][15][16][17] by many workers. However, all these studies have remained confined to a limited number of transitions until the work of the Opacity Project (OP) [10].…”

Section: Introductionmentioning

confidence: 99%

OSCILLATOR STRENGTHS FOR DIPOLE-ALLOWED FINE-STRUCTURE TRANSITIONS IN Si II

Nahar

1998

Atomic Data and Nuclear Data Tables

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“…For the 3s23d 'D-3s24f 'F0 multiplet there have also been considerable discrepancies between theoretical Our 4p 'Po decay curves were decomposed into two exponentials the steepest of which yields a lifetime of 9.1 f 0.5 ns. This value confirms the previous beam-foil result of Berry et al [ 2 ] . Agreement is very satisfactory also with the emission measurements of Hey [37] and Schulz-Gulde [38].…”

Section: Siiisupporting

confidence: 93%

“…Our sensitivity and spectral resolution were better than in the early work of Berry et al [2] and several Si I lines were therefore sufficiently strong to allow decay measurements.…”

Section: Resultsmentioning

confidence: 80%