Knowledge Bank

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 $A~2E\prime \prime$ and $B~2E\prime$ states, suggesting that these states cannot be described by conventional Jahn-Teller hamiltonians. Our previous moderate resolution spectra of the forbidden $A~2E\prime \prime \leftarrow X~2A2\prime$ 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$\mathrm{<mrow\; data-mjx-texclass="ORD">0</mrow>}$ level can only be accessed via the weak $410$ hot band. Contour analysis of the partially resolved rotational structure could not definitively establish whether the zero-point averaged geometry has $D3h$ or $C2v$ symmetry. We report the first rotationally resolved spectrum of the $410$ vibronic band of NO$3$ recorded by diode laser spectroscopy, using off-axis Integrated Cavity Output Spectroscopy (ICOS).