Photodissociation dynamics of HNF. I. Ab initio calculation of global potential energy surfaces, vibrational energies, and wave functions

Abstract

Articles you may be interested inA global ab initio potential energy surface for HNO (a 3 A″) and quantum mechanical studies of vibrational states and reaction dynamicsThe HOOH UV spectrum: Importance of the transition dipole moment and torsional motion from semiclassical calculations on an ab initio potential energy surface Photodissociation of HOBr. I. Ab initio potential energy surfaces for the three lowest electronic states and calculation of rotational-vibrational energy levels and wave functions Three-dimensional potential energy surfaces for the X 2 AЉ and à 2 AЈ states of HNF are reported in the present paper. The ab initio calculations are carried out at the multireference configuration interaction ͑MRD-CI͒ level of theory employing a large basis set. The X 2 AЉ potential surface possesses a deep potential well. Both surfaces have a bent equilibrium, at approximately 100 deg for the ground state and at about 125 deg for the excited one. The two electronic states become degenerate at the linear geometry. Variational calculations for the vibrational energies and the corresponding wave functions have been performed on three-dimensional fitted potential energy surfaces. The first 101 levels of the X 2 AЉ state and the lowest 51 levels of the à 2 AЈ manifold are reported, and their vibrational modes are assigned on the basis of the nodal structure of the corresponding wave functions. The à 2 AЈ vibrational states consist of well-defined polyads with polyad quantum number Pϭ3 1 ϩ 2 ϩ 3 , where 1 Ϫ 3 are the H-N stretching, bending, and N-F stretching quantum numbers, respectively. The calculated barrier height, vertical and adiabatic excitation energies, as well as the dissociation limits, agree satisfactorily with the available experimental data. This underlines that the overall accuracy of the potential energy surfaces is good.