Search

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.

Strong absorption bands exist in propane, n-butane, and isobutane in the 3.8 micrometer DF (deuterium flouride) laser spectral output region. Spectral scans of pure atmospheres of these gases were made using a spectrophotometer to obtain moderate resolution data. Long-path absorption cell measurements were made using five DF laser output wavelengths to obtain high resolution data for the three gases. The absorption cell concentrations of the gases used, 150 to 450 mtorr, were buffered to 760 torr with nitrogen. Results show that DF radiation is attenuated by a few percent per km when propane or butane concentrations are a few ppm.

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 Fabry-Perot etalon is used to identify the relative wavelengths of individual spikes in the long-pulse output of a homogeneously broadened, solid-state laser. This identification is accomplished by positioning one side of a low finesse etalon bandpass such that it is coincident with the laser output. Different wavelength spikes experience different attenuations on passing through the etalon, thus enabling a relative wavelength determination from the etalon transmission value. The etalon is incorporated into a real-time minicomputer controlled measuring system capable of storing, analyzing, and displaying various parameters encountered in laser interaction studies. By utilizing the narrow spectral width of individual laser spikes ( 0.0001 nm) and the large number of different wavelength spikes available in a single long pulse (tens to hundreds), many high-resolution spectral data points can be obtained within the period of one laser shot ( 4 ms). Experimental results of the transmission of erbium: YAG laser radiation in a methane-enriched atmosphere are shown to illustrate one use for the system. This technique provides an accurate means of studying the interaction and propagation nature of certain solid-state lasers used by the Army. The causes of degradation in Army laser systems may be studied with a higher degree of precision, thereby allowing possible minimization or elimination of any such effects. (Author)

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.