Faint OH (nu '=10), (OH)-O-17, and (OH)-O-18 emission lines in the spectrum of the night airglow

We co-added night-sky spectra, recorded as by-products of exposures with th e 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 ove r the wavelength range 5720-8810 Angstrom. On this very high signal-to-nois e ratio spectrum, OH emission lines from the upper vibrational level nu' = 10, previously undetected in the night airglow, were measured and identifie d. Estimates are made for the relative population of OH (nu' = 10), and pos sible secondary mechanisms exciting this level are discussed. Also, lines o f the isotopic molecules (OH)-O-18 and (OH)-O-17 were detected and measured , and the relative populations of these heavy isotopomers are discussed. Li nes of the isotopic molecule OD were not detected, for reasons that are dis cussed, but predicted wavelengths of such lines were calculated and are lis ted for possible future use with even better signal-to-noise ratio spectra, preferably at longer wavelengths.