The B-Component of the Transition Moment for the v2 Band of Nitric Acid Vapor

Abstract

Atmospheric measurements of nitric acid are relevant both in the troposphere, where it is a precursor of inorganic free radicals as well as of nitrates and aerosols1, and in the stratosphere2, where it is a principal repository of odd nitrogen3,4. Single frequency laser detection offers the possibility of distinguishing nitric acid from other atmospheric species if the effective extinction coefficient for a given laser line is known; such information on more than one line heightens the discrimination. Recently, the constants of the Hamiltonian for this band have been published5, so that the transition frequencies and relative line strengths may be calculated. This information has been combined with transmittance data at four different CO laser frequencies which are coincident with the v2 band of nitric acid such that the extinction coefficient is determined for each laser frequency. In addition, the b-component of the transition moment for the band is found at each CO laser line used; these values are consistent among themselves and overlap the earlier determination of Goldman et al. 6 within the quoted uncertainties.