Studies of $NO_{2}$ by LIF and bolometric detection

Abstract

$NO_{2}$ is a small molecule which, although made up of three well-known atoms, behaves in such a manner that it is sometimes spoken of as a perverse molecule. The vibrational structure of the visible absorption spectrum of $NO_{2}$ is dominated by a strong conical intersection between the potential energy surface of the electronic ground state $\tilde{X}^{2}A_{1}$ and of the first electronically excited state $\bar{A}^{2}B_{2}$. From the study of their LIF excitation spectrum, Jost and coworkers [J. Chem. Phys. 95 (8), 5701-5718, (1991)] concluded there was "quantum" chaos in the distribution of vibronic origins in the $16000 cm^{-1}$ to $25000 cm^{-1}$ range. In our laboratory we excite a supersonically cooled beam of $NO_{2}$ molecules with a linear tunable dye laser and a Ti:Sapphire ring laser. This enables us to investigate directly the region where the vibronic chaos will start to take place $(10000 cm^{-1} to 15000 cm^{-1})$. The fluorescence is detected using a photomultiplier. In addition, we are able to detect the molecular beam using a bolometer. With this we hope to bring some order into the chaos.