Effects of oxygen addition on pressure-broadened water-vapor absorption in the 10-microm region

We have measured the monochromatic transmittances of pressure-broadened room-temperature water vapor samples at five laser frequencies of the CO(2) laser in the 10.4-microm band. Three different buffer gases were used. They were pure nitrogen, an 80:20 mixture of nitrogen and oxygen, and a 60:40 mixture of nitrogen and oxygen. The measurements at the five laser lines imply that oxygen is a less efficient broadener than nitrogen. The ratio of the oxygen-broadening coefficient to the nitrogen-broadening coefficient was measured to be 0.75 based on the data at the R(20) laser line. Results of this study demonstrate that pure nitrogen should not be used as a broadener for atmospheric modeling of monochromatic transmittances in the laboratory.