DIODE-LASER MOLECULAR BEAM SPECTRUM OF THE $\nu_{2}$ NO STRETCHING BAND OF CHLORINE NITRATE

1. W. Bell, G. Duxbury and D. D Stuart. J. Mol. Spectrosc. 152, 283 (1992) 2. R. D Suenram and F. J. Lovas, J. Mol. Spectrosc. 105. 351 (1984).Author Institution: Molecular Physics Division, NIST; Instituto de Estructura de la Materia, C.S.I.C.; Instituto de Estructura de la Materia, Dupont Central Research and Development LaboratoryChorine nitrate serves as a temporary reservoir of both chlorine and odd nitrogen in the stratosphere since it is formed by the reaction of $NO_{2}$ and CIO and removes CI atoms from ozone destructive reactions, Unresolved IR spectra of this molecule have been recorded by several laboratories; however, partially resolved rotational spectra are reported in only one study, that of the $\nu_{4}$ band at $779 cm^{-1 1}$. Complete spectral resolution of $CINO_{3}$ at room temperature is hindered by numerous “hot bands” origination mostly from levels of the very low frequency torsional band. The goal of this work is to obtain the spectroscopic constants for the $\nu_{2}$ band at $1293 cm^{-1}$ at low temperatures in a supersonic jet where the ``hot band” lines are suppressed in order to model its strong Q-branch feature at stratospheric temperatures. A molecular beam system coupled with a diode laser spectrometer was used in this study. The sample used was prepared by the reaction of CIF with dry nitric acid and purified by trap-to-trap distillation. About $10% CINO_{3}$ was mixed with argon. The molecular beam was produced by passing this mixture through a 1 inch pulsed slit nozzle. The laser beam was passed through the jet 6 times t increase the absorption path length. Although we have only preliminary results at this writing the $\nu_{2}$ band appears to consist entirely of A-type transitions. The P-and R-branch transitions are completely resolved, and their assignment verified by comparing ground-state combination differences with those calculated using ground-state rotational constants determined by microwave $spectroscopy.^{2}$ The Q-branch region consists of a series of subband Q-branches in which the J structure is unresolved; however the profile of these Q-branches can be reproduced using the spectroscopic constants obtained from the P- and R-branch regions. Transitions with J up to 22 and $K_{a} \leq 11$ have been observed. Comparison of calculated and observed spectra indicates that the beam temperature is about 15 K