Ab initio calculations for the ground state of nitrosomethane and the non-vertical n_.π* excitation energy

The molecular potential energy of nitrosomethane has been computed by SCF CI methods along three coordinates involving the CN and NO bond lengths and their bond angle. These potential energy curves may be used for force constant calculations. The vertical n_.p* excitation energy into the lowest ^tA? state was calculated to be 17 030 cm^-1. Corrections due to geometry changes upon electronic excitation imply an upper limit of 14 530 cm^-1 for the non-vertical separation energy of the two potential energy minima. This is in excellent agreement with the experimental origin of the visible spectrum at 14 408 cm^-1. © 1979.