Ab initio description of the structure and dynamics of the nitrosomethane molecule in the first excited singlet and triplet electronic states

Electronic structure of the low-lying excited states of the CH3NO molecule is considered. The detailed analysis of the first excited triplet and singlet states of this molecule is performed by different ab initio methods to estimate equilibrium geometry, barriers to internal rotation, harmonic frequencies, and adiabatic transition energies. Anharmonic vibrational approximations are also considered. The multidimensional VibSCF scheme and the 1-D variational method for the section of the potential energy surface along the torsion coordinate are used. Theoretical results are found to be in good agreement with experimental data. (C) 2003 Wiley Periodicals, Inc.