Remote Mapping of Vegetation and Geological Features by Lidar in the 9-11-mum Region.

We report examples of the use of a scanning tunable CO(2) laser lidar system in the 9-11-mum region to construct images of vegetation and rocks at ranges as far as 5 km from the instrument. Range information is combined with horizontal and vertical distances to yield an image with three spatial dimensions simultaneous with the classification of target type. Object classification is based on reflectance spectra, which are sufficiently distinct to allow discrimination between several tree species, between trees and scrub vegetation, and between natural and artificial targets. Limitations imposed by laser speckle noise are discussed.

Quantitative chemical identification of four gases in remote infrared (9-11 mum) differential absorption lidar experiments.

A combined experimental and computational approach utilizing tunable CO(2) lasers and chemometric analysis was employed to detect chemicals and their concentrations in the field under controlled release conditions. We collected absorption spectra for four organic gases in the laboratory by lasing 40 lines of the laser in the 9.3-10.8-mum range. The ability to predict properly the chemicals and their respective concentrations depends on the nature of the target, the atmospheric conditions, and the round-trip distance. In 39 of the 45 field experiments, the identities of the released chemicals were identified correctly without predictions of false positives or false negatives.

Development of a scanning, solar-blind, water Raman lidar.

The need for an instrument capable of measuring water-vapor fluxes over mixed canopy and large areas has long been recognized. Such a device would greatly enhance the study of evapotranspiration processes and has great practical value for water management. To address this problem, a scanning water Raman lidar has been designed and constructed. Analytical methods have also been developed to take advantage of the type of information that this lidar can generate. The lidar is able to measure the absolute water content and calculate the evaporative flux quickly over relatively large areas. This capability provides new opportunities for the study of microscale atmospheric processes. The variogram data indicate that the spatial sampling size must be of the order of 10 m if fluxes and scalars are to be properly represented. Examples of data are presented.

Gas temperature and density of UF(6) determined by two-wavelength UV absorption.

The new technique of Wampler and Gentry for determining the temperature and density of a gas by measuring UV gas absorption at two wavelengths [F. B. Wampler and R. A. Gentry, J. Appl. Phys. 52, 1583 1981)] has been applied to gaseous UF(6). At 266 nm the absorption cross section sigma of UF(6) appears to be constant, sigma = (1.15 +/- 0.01) 10(-18) cm(2) from 0-100 degrees C. The absorption cross section at 245 nm over the same temperature range may be represented with the empirical polynomial sigma = [1.37 +/- 0.05 + (9.7 +/- 1.5) 10(-3). T - (4.2 +/- 1.1)10(-5). T(2)] 10(-18) cm(2), where T is in degrees Celsius. Differences in (dsigma/dT)lambda at 266 and 245 nm allow both UF(6) temperature and density to be determined by UV absorption measurements. The strengths and limitations of this technique are discussed.

High-energy optically pumped molecular lasers in the 13- and 16-microm regions.

This paper describes the construction of an optically pumped laser device. The device utilizes a line-tunable CO2 TEA laser as a source to optically pump a cell which is capable of cooling candidate laser gases down to approximately 150 degrees K. Laser outputs of 750 mJ in the 13-microm region and 100 mJ in the 16-microm region are obtained by pumping NH3 and CF4 respectively with 10 J of CO2 laser radiation. The measured conversion efficiencies are 15% for NH3 and 3% for CF4. These lasers can be used to photodissociate polyatomic molecules and are attractive sources for practical laser isotope separation.