UV Raman Cross Sections in Nitrogen

Abstract

In an effort to resolve ambiguities concerning nitrogen's vibrational (Q-branch) Raman cross section at wavelengths near ∼300 nm, a series of measurements were carried out in the region between 282 and 355 nm. Members of our group have employed nitrogen Raman as a means of calibrating the detection efficiency of a ballon-borne lidar system used to measure stratospheric OH. The only known measurement in the region of interest (at 300 nm) displayed a factor-of-two enhancement over that expected theoretically, thereby introducing a significant uncertainty into the measurement. Nitrogen cross sections were measured at 282 and 306 nm, where uncertainty existed between theory and experiment, and at 355 nm, where good agreement was known to exist. As a check upon the technique, vibrational (Q-branch) Raman cross sections in methane and oxygen were also measured.