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D. E. Osterbrock, R. P. S. Stone, A. A. Misch (UCO/Lick Obs./UCSC)
High-resolution spectra were obtained with the Hamilton Echelle Spectrograph and the Coude Auxiliary Telescope (24-in diameter) of Lick Observatory, to check the tentative identification by Osterbrock and Martel (1992) of Li I \lambda6708 in the night sky above San Jose. Spectra were taken with the CAT throughout one night in fall 1999, in successive exposures pointing low in the west over San Jose, at the zenith, and low in the east, 45 min each. The co-added west spectrum had 3 hr total exposure, the other two 2.25 hr each. They show conclusively that the line arises in San Jose, and the measured wavelength, \lambda6708.88, is in good agreement with the average \lambda6707.81 or the weighted average \lambda6707.84 of the Li I doublet. This feature is not present in sky spectra taken at Mauna Kea with HIRES on the Keck I telescope, and clearly results from light pollution. The blend is noticeably broadened, presumably by pressure broadening, with FWHM 1 Åand FW0I 3 Å.
As is well known, very strong Hg I and Na I, greatly broadened and with strong narrow cores, from high- and low-pressure sodium lamps, are present. The lithium is no doubt an impurity in them. Several other weaker Na I lines have been measured and identified as well.
K I \lambda7699 is present in the San Jose sky spectrum, no doubt also an impurity in the sodium lamps. The other component of this doublet is known to be absorbed by atmospheric O2. In addition, many strong lines of Sc I have been identified, clearly from metal halide lamps, some of which contain scandium. Many lines of Ne I have also been measured and identified, probably from signs in San Jose.