UPPER LIMIT FOR LITHIUM IN MERCURYS ATMOSPHERE

High-resolution spectra of Mercury show no evidence of emission at the wavelength of the lithium resonance doublet, 6708 Angstrom. Observati ons were made with the 1.5-m telescope at the Catalina Observatory, ne ar Tucson, Arizona, with the LPL echelle spectrograph and cooled CCD c amera system. With an rms noise level of similar to 0.1% we set an upp er limit for the Li vertical column abundance <8.4 x 10(7) atoms cm(-2 ), and the Li/Na ratio is <5.6 x 10(-4). (C) 1996 Academic Press, Inc.