A theoretical study on the potential surfaces of the lower electronic states of HCO

The results of ab initio potential-energy surface calculations are presented for the lowest four doublet states of HCO. A conical Jahn–Teller intersection was found between the lowest two 2A′ surfaces. The equilibrium geometries of the lowest two quartet states were also calculated. Discussion is primarily focused on the assignment of the hydrocarbon flame bands. The A bands of the hydrocarbon flame bands are assigned as a ?2A′→?2A′ transition which concurs with Dixon’s speculation. As for the ? state which is the origin of the B bands, the most probable state is the bent second 2A″ state which is described by the configuration (6a′)2(7a′)2(1a″)1.