Quantum mechanical study of the CH(v=2) overtone in 30-mode benzene

Abstract

The results of large-scale quantum mechanical calculations of the CH(v=2) 1st overtone spectrum for 30-mode benzene are reported. This overtone was chosen for investigation because of its high degree of fragmentation and resulting complexity compared to spectra for the fundamental and higher overtones. These calculations use the best available ab initio force field supplemented by higher-order terms for the CH stretch–wag interaction. The dynamical calculations were conducted in large active spaces with 12 000 or 16 000 vibrational basis functions. The recursive residue generation method was used to compute residues (intensities) and eigenvalues. From these quantities, the lineshape function, survival probabilities, and vibrograms were computed. Wherever possible, these results were compared to experimental overtone spectra and to other computational results.