Oscillator strengths for AsI-III

Ganas, P. S.

doi:10.1051/aas:2000191

Cited by 8 publications

(8 citation statements)

References 17 publications

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“…As discussed in Section 3.1, the oscillator strength for the As ii transition at 1263.8Å has not been experimentally verified. Various theoretical determinations of the f -value range from 0.18 to 0.35 (e.g., Ganas 2000), and have a mean not very much different from the value of 0.259 adopted by Morton (2000) and used in this investigation. The oscillator strength would need to be a factor-of-three larger than the Morton (2000) value to account for the 0.47 dex discrepancy between the initial interstellar abundance of As (implied by the least-squares fit) and the solar system abundance.…”

Section: Survival Analysismentioning

confidence: 75%

Abundances and Depletions of Neutron-capture Elements in the Interstellar Medium

Ritchey

Federman

Lambert

2018

ApJS

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We present an extensive analysis of the gas-phase abundances and depletion behaviors of neutron-capture elements in the interstellar medium (ISM). Column densities (or upper limits to the column densities) of Ga ii, Ge ii, As ii, Kr i, Cd ii, Sn ii, and Pb ii are determined for a sample of 69 sight lines with high-and/or mediumresolution archival spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. An additional 59 sight lines with column density measurements reported in the literature are included in our analysis. Parameters that characterize the depletion trends of the elements are derived according to the methodology developed by Jenkins. (In an appendix, we present similar depletion results for the light element B.) The depletion patterns exhibited by Ga and Ge comport with expectations based on the depletion results obtained for many other elements. Arsenic exhibits much less depletion than expected, and its abundance in low-depletion sight lines may even be supersolar. We confirm a previous finding by Jenkins that the depletion of Kr increases as the overall depletion level increases from one sight line to another. Cadmium shows no such evidence of increasing depletion. We find a significant amount of scatter in the gas-phase abundances of Sn and Pb. For Sn, at least, the scatter may be evidence of real intrinsic abundance variations due to s-process enrichment combined with inefficient mixing in the ISM.The primary aim of our extensive search of the HST /STIS archive was the identification of sight lines showing significant absorption from As ii λ1263, Cd ii λ2145, Sn ii λ1400, and Pb ii λ1433. While these lines are the principal transitions used to study these species in diffuse interstellar clouds, they are only rarely seen in UV spectra (although Sn ii λ1400 is somewhat more common than the others). To construct our sample, we started by examining the sight lines analyzed by R11 in their survey of B ii absorption in the diffuse ISM. The absorption features sought in the present survey are expected to have similar strengths compared to B ii λ1362. Moreover, for each of the directions studied by R11, we have detailed knowledge of the line-ofsight component structure from moderately strong absorption lines of dominant ions such as O i λ1355. This facilitates the search for weak features from other dominant ions that are expected to exhibit similar absorption profiles. We also expanded our search by examining the available STIS data for all other sight lines in the HST archive with the necessary wavelength coverage, considering observations acquired using either the high-resolution gratings (E140H and E230H) or the medium-resolution gratings (E140M and E230M) of the STIS FUV and NUV Multi-Anode Microchannel Array (MAMA) detectors. We noted any sight lines that showed apparent absorption from one or more of the four principal lines of interest at a velocity similar to that of O i λ1355. This process resulted in 14 sight lines being added to our initial list of 55...

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Section: Survival Analysismentioning

confidence: 75%

Abundances and Depletions of Neutron-capture Elements in the Interstellar Medium

Ritchey

Federman

Lambert

2018

ApJS

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“…The contribution by transitions to levels 4p 4 3 P could be taken into account using information about the branching ratios. Unfortunately, no relevant information is contained in [18,20], and the accuracy of the results of numerical study [19] (at least for forbidden transitions) is in doubt for reasons given above. We turn to the OEF structure (Fig.…”

Section: Results and Their Discussionmentioning

confidence: 99%

Dissociative excitation of selenium atoms in collisions of electrons with Se2 molecules

Smirnov

2006

High Temp

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The dissociative excitation of selenium atom by electron impact is investigated for the first time under conditions of narrow composition of molecular beam. The thermal destruction of heavy Se n molecules is used to obtain a beam with prevailing Se 2 molecule. Seventeen cross sections of dissociative excitation of SeI are measured at electron energy of 50 eV. Possible reactions of formation of excited selenium atoms in e-Se 2 collisions are discussed.

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“…In addition, spectra of the gallium-like ions excited by low-inductance sparks and laser-produced plasmas were observed [10]. Oscillator strengths for excitations of As I-III are calculated using a semiemprical analytic independent-particle-model [11]. Also the energy levels and observed spectral lines of Krypton, Kr I through Kr XXXVI have been studied [12].…”

Section: Introductionmentioning

confidence: 99%

Atomic Data and Laser Transitions in as - Like Gallium

Refaie¹

2016

AJPA

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Abstract:Fine structure calculations of the energy levels, the wavelengths, the oscillator strengths, log gf and the transition probabilities for transitions among the terms belonging to 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 ns, n=5-6, 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 np, n=4-6, 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 nd, n=4-6 and1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 nf, n=4-6 configurations of As (III) have been calculated using configurations interaction Cowan atomic structure code. Our calculated values for the above mentioned quantities have been compared with the corresponding experimental data and other theoretical calculations where a satisfactory agreement is found. We also report on some unpublished values for energy levels, oscillator strengths and transition probabilities for As like gallium. These atomic data are taken as the basis for studying laser transitions between levels of As(III). Excitation rate coefficients of As like gallium are calculated using the analytical formulas of Vriens and Smeets (1980) and with considering using the collisional radiative model code CRMO of Allam (2006). A simple modification to these formulas has been included by introducing effective quantum numbers. The energy values, the radiative data and rate coefficients are then used to calculate the population densities by solving the coupled rate equations. Among these calculations positive gain coefficients are found at three selected values of electron temperature, namely 7.087 eV, 14.147 eV and 21.261 eV which are displayed as a function of the electron impact density.

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Oscillator strengths for AsI-III

Cited by 8 publications

References 17 publications

Abundances and Depletions of Neutron-capture Elements in the Interstellar Medium

Abundances and Depletions of Neutron-capture Elements in the Interstellar Medium

Dissociative excitation of selenium atoms in collisions of electrons with Se2 molecules

Atomic Data and Laser Transitions in as - Like Gallium

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