Ground state dynamics of NO3: Multimode vibronic borrowing including thermal effects

Abstract

The X ²A₂^’ band of the photoelectron spectrum of NO⁻₃ is theoretically calculated in the framework of a multimode vibronic coupling model. Linear coupling between and within the X ²A₂^’ and the B ²E’ electronic states of NO₃ is found to be the important mechanism governing the dynamics. The necessary coupling constants are obtained from the ionization potentials of NO⁻₃ calculated at different geometries using ab initio Green’s functions. Comparison of the theoretical with experimental results [A. Weaver, D. W. Arnold, S. E. Bradforth, and D. M. Neumark, J. Chem. Phys. 94(3), 1740 (1991)] for the PE spectrum shows good agreement if a temperature of the NO⁻₃ anion of 455 K in the experiment is assumed. A general theoretical treatment of thermal effects in vibronically coupled electronic states is presented. The ground electronic state potential surface of NO₃ is discussed in the framework of the vibronic coupling model. A shallow minimum at a C_2v geometry with a barrier height of 0.006 eV relative to the minimum energy D_3h configuration is found. It is too weak to deform the effective geometry of the molecule from D_3h to C_2v. Mode‐mode coupling is found to play a relevant role in the ground electronic state of NO₃, in general.