Potential energy function and vibrational states of N2CO+

Abstract

A six-dimensional potential energy function (PEF) for the electronic ground state of N2CO+ (X 2A′) has been generated by electronic structure calculations using the restricted open shell coupled cluster RCCSD(T) approach. The ion has a planar trans equilibrium structure with: RNN=1.106 Å, RNC=1.905 Å, RCO=1.127Å, θNNC=175.3°, and θNCO=129.1°. Variational calculations of the vibrational states (J=0) have yielded the following anharmonic wavenumbers for the fundamentals: ν1 (NN stretch) 2287.2, ν2 (CO stretch) 2071.0, ν3 (CN stretch+NCO bend) 546.9, ν4 (CN stretch+NCO bend) 215.2, ν5 (in-plane NNC bend) 123.4, ν6 (out-of-plane NNC bend) 133.8 (all values are in cm−1). For fixed equilibrium coordinates except one, the barriers to linearity have been calculated to be 8 cm−1 for the NNC and 2260 cm−1 for the NCO moieties, the torsional barrier to be 35 cm−1. It has been found that the ν3 and ν4 modes are strongly coupled, the in-plane ν5 and out-of-plane ν6 bending modes possess an inverse anharmonicity and fall into clusters. Using complete active space self-consitent-field CASSCF approach on the collinear cuts of the PEF for low-lying excited states several conical intersections between the Π2 and the Σ+2 states have been located.