Fermi polyads and rovibronic spectrum of the X 2Πg state of BO2

Abstract

Using ab initio electronic structure calculations, the three dimensional potential energy functions have been generated for the X 2Πg electronic ground state of BO2 . Spin–rovibronic energy levels have been calculated up to 4000 cm−1, Ka=3 by a variational approach accounting for full dimensionality, anharmonicity, rotation–vibration, spin, and Renner–Teller coupling. Almost all of the approximately 70 experimentally known vibronic levels up to 4000 cm−1 have been reproduced to within 10 cm−1. All vibronic energy levels (J=P) up to 4000 cm−1 are given for the 11BO2 isotope. From the composition of the rovibronic wave functions for the Fermi polyads new assignments were made. The anharmonic resonances have been investigated in the framework of a complete three dimensional Brown–Joergensen Hamiltonian for quartic force fields in dimensionless normal coordinates.