Study on local mode vibrations of molecular vibrational excitation states in CH_4, SiH_4 and GeH_4 with quasiclassical trajectory method

摘要

By using the quasiclassical trajectory method, changes of normal and local mode vibrational excitation energies with time are investigated for XH_4 (X=C, Si, Ge) molecules. The results demonstrate that in a CH_4 molecule the coupling between C—H stretching vibration and H—C—H bending vibration is relatively large so that the energy transfer is fast; while in SiH_4 or GeH_4 molecules this coupling is relatively small and thus an obvious energy relaxation is observed. This implies that there exists approximate local mode vibrations for certain vibrational excitation states.