Line widths and intensities in H 2O-CO 2 mixtures—I. An experimental study on the 6·3 μ band of water vapor

Abstract

Measurements are reported of rotational half-widths and line intensities in H 2O-CO 2 mixtures. Room-temperature data are presented in the long-wave length wing of the v 2-fundamental of water vapor with carbon dioxide used as inert broadening agent. The experiments were performed with mixtures of very small amounts of water vapor (2–10 mm Hg) and about 2 to 5 atm of carbon dioxide in an externally adjustable 10 m gas cell with path lengths from 1·25 m to 10 m. The spectral resolution was 0·4 cm -1 or better. The CO 2-broadened half-widths appear to be approximately equal to 0·25 cm -1 atm -1, which are about half as large as self-broadened half-widths (0·5 cm -1 atm -1) and nearly twice the estimates for nitrogen (or air)-broadened half-widths (which are about 0·1 to 0·13 cm -1 atm -1). The line strengths for the lines reported here are smaller by about a factor of two than those given by Sakai.