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A line tunable deuterium fluoride laser was used to measure the pressure dependence of the water vapor continuum absorption at 25 degrees C in the 3.5-4.0-microm spectral region. From measurements of the absorption of 14.3 Torr of deuterium depleted water vapor buffered by several air-broadening pressures, an unexpectedly small foreign-to-self-broadening coefficient of 0.011 with a factor of 2 uncertainty as well as an unusually strong self-contribution for the water vapor continuum absorption were observed. These measurements can be used to infer contributions to the water vapor continuum in the 3-5-microm window from both far wing and aggregate-water-molecule type absorptions.

Water vapor absorption coefficients are reported for nine HF laser wavelengths ranging from 3418.1600 cm(-1) to 3788.2253 cm(-1) for temperatures ranging from -18 degrees C to 25 degrees C. Pure water vapor as well as airbroadened (N(2)/O(2)) water vapor absorptions were measured at pressures from less than 1-764 Torr with some of the air-broadened data being used to extract effective self-to-foreign-broadening parameters in the vicinity of the laser frequencies. Limited data were also collected on O(2)-broadened water vapor absorption as well as pure and air-broadened CO(2) absorption. The CO(2) data agree reasonably well with theoretical predictions; but the air- and O(2)-broadened water vapor data show greater absorption than theoretically predicted and seem to imply a super Lorentz/Voigt line shape for H(2)O.

Measurements of water vapor continuum absorption in the 3.5-4.0-microm 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 23 degrees C and 65 degrees C with 14.3 Torr and 65 Torr of water vapor, respectively, buffered to 760-Torr total pressure by an 80/20 mixture of N(2)/O(2). Both natural water and a special sample of deuterium depleted water (one-fiftieth the normal concentration) were used. The 65 degrees C results agree with previous measurements by other workers. The 23 degrees 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 (>/=65 degrees C) of others.

A new method of quantitatively measuring the absorption of atmospheric dust or other particulate matter is described. The system uses a differential-spectrophone KBr pellet technique and should ultimately prove useful from the uv to the far ir wavelength region. Preliminary measurement data on atmospheric dust, quartz, and soot are presented at 1.06-microm, 9.6-microm, and 10.6-microm wavelengths.