Calculations of stretching vibrational energy levels of the CH3I molecule by a nonlinear model

A nonlinear model, i.e. the quantized discrete self-trapping equation, is a pplied to calculate the highly excited CH stretching vibrational energy lev els of the CH3I molecule in the liquid phase at the electronic ground state up to n=8. The obtained results agree well with the experimental data and with those obtained from local mode model calculations. We note that the do minant feature of the methyl CH stretching vibrational energy levels of the CH3I molecule is a pattern of local mode pairs. When n greater than or equ al to 7, all the vibrational energy of the CH3 group can nearly be localize d on a single CH bond.