Knowledge Bank

Well-known as an important intermediate in atmospheric chemistry, the nitrate radical (NO$3$) has been extensively studied both experimentally and theoretically. The three energetically lowest electronic states ($X~$ $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}A2\prime$, $A~$ $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}E\prime \prime$, and $B~$ $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}E\prime$) are strongly coupled by vibronic interactions and hence it is a textbook molecule for understanding the coupling between nearby potential energy surfaces. Such coupling has been treated in considerable detail theoretically., \underline{\textbf{126}}, 134309 (2007)}} However, corresponding experimental characterization of the interaction is much less detailed. The experimental results primarily consist of IR measurements of vibrational transitions in the ground state., \underline{\textbf{93}}, 951 (1990)}}, \underline{\textbf{231}}, 193 (1998)}} In addition, the electronically forbidden $A~$-$X~$ transition has been observed in ambient temperature CRDS studies., \underline{\textbf{122}}, 224305 (2005)}} To understand both the Jahn-Teller and pseudo Jahn-Teller coupling in the molecule, further measurements are required with different selection rules and/or higher resolution to resolve the rotational structures of different transitions. In our group, a high-resolution (source $\Delta \nu \approx$ 100 MHz in NIR region), jet-cooled CRDS system$, and T. A. Miller, {\textit{Phys. Chem. Chem. Phys.}, \underline{\textbf{8}}, 1682, (2006)}} can be applied to rotationally resolve the electronically forbidden $A~$-$X~$ transition. Furthermore, our high-resolution LIF/SEP system (source $\Delta \nu \approx$ 100 MHz) can provide the direct, rotationally resolved measurements of the $B~$-$X~$ and $B~$-$A~$ transitions by operating in the LIF and SEP modes respectively. Such data can provide unambiguous spectral assignments in the $X~$, $A~$ and $B~$ states.