Faint OH (ν′ = 10), 17OH, and 18OH Emission Lines in the Spectrum of the Night Airglow1,1Lick Observatory Bulletin 1380. 22Based on observations obtained at the W. M. Keck Observatory, which is operated by the California Institute of Technology and the University of California.

Abstract

ABSTRACTWe co‐added night‐sky spectra, recorded as by‐products of exposures with the high‐resolution echelle spectrograph (HIRES) of the Keck I 10 m telescope on stars and quasars over a period of approximately 21 / 2 years, to obtain a resultant spectrum with total exposure time ranging from 120 to 24 hr over the wavelength range 5720–8810 Å. On this very high signal‐to‐noise ratio spectrum, OH emission lines from the upper vibrational level ν′ = 10, previously undetected in the night airglow, were measured and identified. Estimates are made for the relative population of OH (ν′ = 10), and possible secondary mechanisms exciting this level are discussed. Also, lines of the isotopic molecules 18OH and 17OH were detected and measured, and the relative populations of these heavy isotopomers are discussed. Lines of the isotopic molecule OD were not detected, for reasons that are discussed, but predicted wavelengths of such lines were calculated and are listed for possible future use with even better signal‐to‐noise ratio spectra, preferably at longer wavelengths.