NIR OFF-AXIS ICOS SPECTRUM OF THE NITRATE RADICAL: DOES THE VIBRATIONLESS A$^2$E$^{\prime \prime }$ STATE OF NO$_3$ UNDERGO STATIC JAHN-TELLER DISTORTION?
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Date
2006
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Publisher
Ohio State University
Abstract
The Jahn-Teller effect in the first two excited states of NO$_3$ is poorly understood. There is increasing evidence for relatively strong Jahn-Teller and Pseudo-Jahn-Teller couplings in the $\tilde{A}^2E^{\prime\prime}$ and $\tilde{B}^2 E^{\prime}$ states, suggesting that these states cannot be described by conventional Jahn-Teller hamiltonians. Our previous moderate resolution spectra of the forbidden $\tilde{A}^2E^{\prime\prime}\leftarrow \tilde{X}^2 A_2^{\prime}$ transition revealed further evidence of strong Jahn-Teller interactions, but could not establish if the upper state exhibited static Jahn-Teller distortion. The origin band is strictly forbidden by Herzberg-Teller selection rules, and the 0$^{0}$ level can only be accessed via the weak $4_1^0$ hot band. Contour analysis of the partially resolved rotational structure could not definitively establish whether the zero-point averaged geometry has $D_{3h}$ or $C_{2v}$ symmetry. We report the first rotationally resolved spectrum of the $4_1^0$ vibronic band of NO$_3$ recorded by diode laser spectroscopy, using off-axis Integrated Cavity Output Spectroscopy (ICOS).
Description
Author Institution: Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena CA 91125; Jet Propulsion Laboratory, California Institute of; Technology, Pasadena, CA 91109; Department of Chemistry, University of Texas, Austin, TX, 78712