SUBMILLIMETER-SPECTROSCOPY OF A SUPERSONIC FLOW OF LOW-DENSITY WATER VAPOR.

A spectroscopic method is presented for determining the temperature and density in supersonic flows of low-density gases. The method is based on the measurement of the integrated absorption coefficient and the width of the spectral lines of the rotational spectrum of the H//2O molecule. This method is based on the assumption that the gas flow at the observation point is in rotational equilibrium. This method is used to determine the temperature in a supersonic flow of water vapor (p//0 equals 10 - 16 torr, T//0 equals 288 degree K) in planar, wedge-shaped nozzles (with M equals 1. 3 - 1. 5 at the observation point), on the basis of the 2//0//2-2//1//1 spectral line of the H//2 **1**6O molecule ( lambda equals 0. 3986 mm). The error in the temperature measurements is smaller than 1 degree .