THE $\tilde{X}^{2} A_{1} -\tilde{A}^{2}B_{2}$ CONICAL INTERSECTION IN $NO_{2}$, OR HOW EXPERIMENTS AND THEORY INTERPLAY TOGETHER
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Date
2000
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Publisher
Ohio State University
Abstract
We present a comparison between experimental results (vibronic energies, absorption and LIDFS intensity ratios, rotational constants) and ab-initio calculations (diabatic and adiabatic energies, vibronic matrix elements). The three main inputs required in the analysis of the $\tilde{X}^{2} A_{1} - \tilde{A}^{2}B_{2}$ conical intersection are: i) the diabatic levels of the $\tilde{X}^{2} A_{1}$ state (i. e., the complete set of approximatively 200 low lying levels of the $\tilde{X}^{2} A_{1}$ observed by LIDFS), ii) the diabatic levels of the $\tilde{A}^{2} B_{2}$ state (they are approximately predicted by the ab-initio calculations), iii)the matrix elements of the vibronic interaction, $V_{12}$, between the $\tilde{X}^{2} A_{1}$ and $\tilde{A}^{2} B_{2}$ electronic states. The validity of the simplified form proposed for $V_{12}$, namely ``$\lambda Q_{3}^{\prime\prime}$, will be discussed. The comparison allows to assign some observed vibronic levels, which in return can be used to improve some parameters of the initial ab-initio PESurfaces. Up to now, our analysis is limited to the four lowest polyads of the $\tilde{A}^{2} B_{2}$ state ranging from $9700 cm^{-1}$ to $12300 cm^{-1}$. At higher energy the interactions are stronger, leading to vibronic chaos above $\sim 1700 cm^{-1}$.
Description
Author Institution: Grenoble High Magnetic Field Laboratory, CNRS-MPI; GSMA, UFR Sciences