Atomic and molecular data for observations of the interstellar medium with the hubble space telescope
The high resolution spectrograph on HST, with resolving powers up to 94000 or 3.2 km s−1, is giving us a new look at interstellar absorption lines in the range 1090 to 3350 Å. The high signal-to-noise ratios possible with the digicon detectors provide precise line profiles suitable for studying individual velocity components.
Comparison of these components in different atoms and molecules requires accurate laboratory wavelengths. Their uncertainties are within ±0.002Å for many of the transitions expected to be detected by HST and almost all are known within ±0.02 Å. The notable exceptions are some intersystem transitions, which are mentioned in this paper.
Transition probabilities with 1σ errors within ±0.03 dex and good agreement between theoretical and experimental values are becoming available for many of the resonance lines observable with HST, but many remain to be measured to this accuracy, and some important lines are not yet known within ±0.3 dex. This paper lists those values urgently needed to take full advantage of HST.
KeywordsResonance Line Column Density Hubble Space Telescope Interstellar Absorption High Resolution Spectrograph
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