Knowledge Bank

The $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$E state of NO$3$ is doubly degenerate and is therefore subject to Jahn-Teller (JT) distortion. In the $A~$ state there are two JT active modes, $\nu 3$ and $\nu 4$ ($e\prime$ stretch and in plane bend respectively). Theoretical work has predicted that the JT effect in the $A~$ state should be quite strong and approach the static case (D$\geq$1) where the molecule is permanently distorted to a lower symmetry geometry. A moderate resolution spectrum of the $A~$ state showed a feature that we tentatively assigned as the 3$\mathrm{0<mrow\; data-mjx-texclass="ORD">1</mrow>}$ band based on position and band contour. Using high resolution cavity ringdown spectroscopy we have now obtained a rotationally resolved spectrum of this band. The analysis of this band has been commenced using an oblate symmetric top Hamiltonian with spin-rotation terms. This analysis supports the assignment of this band to the a vibronic component of the 3$\mathrm{0<mrow\; data-mjx-texclass="ORD">1</mrow>}$ band. So far, the spectrum shows no evidence of a large geometric distortion of the molecule. Some lines appear to be split, as was previously observed in the 4$\mathrm{0<mrow\; data-mjx-texclass="ORD">1</mrow>}$ and 4$\mathrm{0<mrow\; data-mjx-texclass="ORD">2</mrow>}$ bands, and the possible sources of this splitting are being investigated.