Vibrational and coherence dynamics of molecules

We {\it analytically} investigate the population and coherence dynamics and relaxations in the vibrational energy transport in molecules. The corresponding two time scales $t_1$ and $t_2$ are explored. Coherence-population entanglement is found to considerably promote the time scale $t_2$ for dephasing and the amplitude of coherence. This is attributed to the suppression of the environment-induced drift force by coherence. Moreover the population imbalance (magnetization) is shown to be significantly amplified with the coherence-population entanglement. Contrary to the previous studies, we exactly elucidate a coherent process by showing $t_1<t_2$. We predict the relaxation of vibrational and orientational dynamics of OH-stretching modes in agreement with the recent experiments, when applied to the water molecules dissolved in D$_2$O. Finally we explore the coherence effect on the heat current at the macroscopic level.