Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Neutral Chlorine

Alkhayat, Rabee B.; Irving, R. E.; Federman, S. R.; Ellis, David; Cheng, Song

doi:10.3847/1538-4357/ab4db6

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…For many of these sight lines, we use observations of the Cl I λ1004, λ1094, or λ1097 transition, available from FUSE spectra, to help constrain the Cl I column density. Experimentally determined fvalues for the Cl I transitions at 1004.7 Å and 1094.8 Å were recently reported by Alkhayat et al (2019). These f-values, from beam-foil experiments, are in good agreement with the empirical f-values derived for these transitions by Sonnentrucker et al (2006).…”

Section: Neutral Chlorinesupporting

confidence: 82%

A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium*

Ritchey

Brown

Federman

et al. 2023

ApJ

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We present a comprehensive examination of interstellar P and Cl abundances based on an analysis of archival spectra acquired with the Space Telescope Imaging Spectrograph of the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. Column densities of P ii, Cl i, and Cl ii are determined for a combined sample of 107 sight lines probing diffuse atomic and molecular gas in the local Galactic interstellar medium. We reevaluate the nearly linear relationship between the column densities of Cl i and H2, which arises from the rapid conversion of Cl+ to Cl0 in regions where H2 is abundant. Using the observed total gas-phase P and Cl abundances, we derive depletion parameters for these elements, adopting the methodology of Jenkins. We find that both P and Cl are essentially undepleted along sight lines showing the lowest overall depletions. Increasingly severe depletions of P are seen along molecule-rich sight lines. In contrast, gas-phase Cl abundances show no systematic variation with molecular hydrogen fraction. However, enhanced Cl (and P) depletion rates are found for a subset of sight lines showing elevated levels of Cl ionization. An analysis of neutral chlorine fractions yields estimates for the amount of atomic hydrogen associated with the H2-bearing gas in each direction. These results indicate that the molecular fraction in the H2-bearing gas is at least 10% for all sight lines with log N ( H 2 ) ≳ 18 and that the gas is essentially fully molecular at log N ( H 2 ) ≈ 21 .

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Section: Neutral Chlorinesupporting

confidence: 82%

A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium*

Ritchey

Brown

Federman

et al. 2023

ApJ

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show abstract

“…For many of these sight lines, we use observations of the Cl i λ1004, λ1094, or λ1097 transition, available from FUSE spectra, to help constrain the Cl i column density. Experimentally determined f -values for the Cl i transitions at 1004.7 Å and 1094.8 Å were recently reported by Alkhayat et al (2019). These fvalues, from beam-foil experiments, are in good agreement with the empirical f -values derived for these transitions by Sonnentrucker et al (2006).…”

Section: Neutral Chlorinesupporting

confidence: 81%

A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium

Ritchey¹,

Brown²,

Federman³

et al. 2023

Preprint

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We present a comprehensive examination of interstellar P and Cl abundances based on an analysis of archival spectra acquired with the Space Telescope Imaging Spectrograph of the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. Column densities of P ii, Cl i, and Cl ii are determined for a combined sample of 107 sight lines probing diffuse atomic and molecular gas in the local Galactic interstellar medium (ISM). We reevaluate the nearly linear relationship between the column densities of Cl i and H 2 , which arises from the rapid conversion of Cl + to Cl 0 in regions where H 2 is abundant. Using the observed total gas-phase P and Cl abundances, we derive depletion parameters for these elements, adopting the methodology of Jenkins. We find that both P and Cl are essentially undepleted along sight lines showing the lowest overall depletions. Increasingly severe depletions of P are seen along molecule-rich sight lines. In contrast, gas-phase Cl abundances show no systematic variation with molecular hydrogen fraction. However, enhanced Cl (and P) depletion rates are found for a subset of sight lines showing elevated levels of Cl ionization. An analysis of neutral chlorine fractions yields estimates for the amount of atomic hydrogen associated with the H 2 -bearing gas in each direction. These results indicate that the molecular fraction in the H 2 -bearing gas is at least 10% for all sight lines with log N (H 2 ) 18 and that the gas is essentially fully molecular at log N (H 2 ) ≈ 21.

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“…However, there have been several significant improvements in oscillator strengths in the two decades since those compilations were published. New experimental f-values are now available for commonly observed transitions of P II (Federman et al 2007;Brown et al 2018), Cl I (Alkhayat et al 2019), Cl II (Schectman et al 2005), Cu II (Brown et al 2009), Ge II (Heidarian et al 2017), and Pb II (Heidarian et al 2015). In addition, empirically derived f-values have been determined for several transitions of Fe II (Miller et al 2007) and Ni II (Jenkins & Tripp 2006;Boissé & Bergeron 2019).…”

Section: Accumulation Of Data From the Literaturementioning

confidence: 99%

The Distribution of Metallicities in the Local Galactic Interstellar Medium*

Ritchey

Jenkins

Shull

et al. 2023

ApJ

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In this investigation, we present an analysis of the metallicity distribution that pertains to neutral gas in the local Galactic interstellar medium (ISM). We derive relative ISM metallicities for a sample of 84 sight lines probing diffuse atomic and molecular gas within 4 kpc of the Sun. Our analysis is based in large part on column density measurements reported in the literature for 22 different elements that are commonly studied in interstellar clouds. We supplement the literature data with new column density determinations for certain key elements and several individual sight lines important to our analysis. Our methodology involves comparing the relative gas-phase abundances of many different elements for a given sight line to simultaneously determine the strength of dust depletion in that direction and the overall metallicity offset. We find that many sight lines probe multiple distinct gas regions with different depletion properties, which complicates the metallicity analysis. Nevertheless, our results provide clear evidence that the dispersion in the metallicities of neutral interstellar clouds in the solar neighborhood is small (∼0.10 dex) and only slightly larger than the typical measurement uncertainties. We find no evidence for the existence of very low metallicity gas (as has recently been reported by De Cia et al.) along any of the 84 sight lines in our sample. Our results are consistent with a local Galactic ISM that is well mixed and chemically homogeneous.

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Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Neutral Chlorine

Cited by 4 publications

References 28 publications

A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium*

A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium*

A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium

The Distribution of Metallicities in the Local Galactic Interstellar Medium*

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