Measurements of water vapor continuum absorption in the 3.5-4.0-gm region are presented. The measurements were made with both long-path absorption cell and spectrophone systems. A deuterium fluoride grating tunable laser was the ir source. Measurements were made at 231C and 65 C with 14.3 Torr and 65 Torr of water vapor, respectively, buffered to 760-Torr total pressure by an 80/20 mixture of N2 /0 2. Both natural water and a special sample of deuterium depleted water (one-fiftieth the normal concentration) were used. The 65°C results agree with previous measurements by other workers. The 23°C results indicate a continuum absorption at this temperature about a factor of 2 larger than expected based on the extrapolation scheme and high-temperature data (265°C) of others.
