Abstract

We have studied the effects of ambient temperature and humidity on laser beam absorption by atmospheric water vapor. A krypton ion laser pumped CW dye laser (Coherent model 599) with a ~1MHz bandwidth was tuned to selected water vapor vibrational absorption lines near 7200 A. A second dye laser (Coherent model 595) was used concurrently for normalization of fluctuations in transmittance due to turbulence. Transmission over a 2km outdoor folded path to a 30” Cassegrain receiver was monitored as a function of psychrometer, thermometer and barometer readings for absorption lines of various ground state rotational energies (fig. 1).