Photodissociation of N₂O: I. Ab initio potential energy surfaces for the low-lying electronic states X ¹A', 2¹A', and 1¹A''

Abstract

Adiabatic potential energy surfaces of the three lowest lying singlet states, X ¹A', 2¹A', and 1¹A'' of N₂O have been computed as a function of the R_N2-O bond distance and the Jacobi angle. The calculations are performed using the complete-active-space self-consistent field (CASSCF) and the multi-reference configuration interaction (MRCI) electronic structure methods. It is shown that there is a wide avoided crossing between the ground, X ¹A', and lowest excited, 2X ¹A', electronic state. This avoided crossing is thought to give rise to a seam of conical intersection at other N-N separations. Both excited state surfaces display important conical intersections at linear geometries. The transition dipole moment surfaces for the two excitation processes ( 2¹A' <--- X¹A' and 1¹A'' <--- X¹A') are also presented. These calculations provide the basic data needed to compute the dynamics of the n₂O + h\nu ---> N₂ + O(¹D) photodissociation process for photon frequencies in the range 5.2 eV (240 nm) to 7.3 eV (170 nm).

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