Zhang Yong, Fujisaki Hiroshi, Straub John E
Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA.
J Phys Chem A. 2009 Apr 2;113(13):3051-60. doi: 10.1021/jp8109995.
The mode-specific vibrational energy relaxation of the amide I' and amide II' modes in NMA-d(1)/(D(2)O)(n) (n = 0-3) clusters were studied using the time-dependent perturbation theory at the B3LYP/aug-cc-pvdz level. The amide modes were identified for each cluster based on the potential energy distribution of each mode. The vibrational population relaxation time constants were derived for the amide I' and II' modes. Results for the amide I' mode relaxation of NMA-d(1)/(D(2)O)(3) agree well with previous experimental results. The energy relaxation pathways were identified, and both intra- and intermolecular mechanisms were found to be important. The amide II' mode was identified in the energy transfer pathways from the excited amide I' mode of NMA-d(1)/(D(2)O)(n) (n = 1-3) clusters. The modes associated with methyl group deformation were found to play a role in the mechanism of energy transfer from both excited amide I' and II' modes. The kinetics of energy flow in the cluster were examined by solving a master equation describing the vibrational energy relaxation process from excited system mode as a multistep reaction with the third order Fermi resonance parameters as the reaction rate constants. The intramolecular energy transfer mechanism was found to dominate the short time energy flow dynamics, whereas the intermolecular mechanism was found to be dominant at longer times.
在B3LYP/aug-cc-pvdz水平上，使用含时微扰理论研究了NMA-d(1)/(D₂O)ₙ（n = 0 - 3）团簇中酰胺I'和酰胺II'模式的模式特异性振动能量弛豫。基于每个模式的势能分布，为每个团簇确定了酰胺模式。推导了酰胺I'和II'模式的振动布居弛豫时间常数。NMA-d(1)/(D₂O)₃的酰胺I'模式弛豫结果与先前的实验结果吻合良好。确定了能量弛豫途径，发现分子内和分子间机制都很重要。在NMA-d(1)/(D₂O)ₙ（n = 1 - 3）团簇的激发酰胺I'模式的能量转移途径中确定了酰胺II'模式。发现与甲基变形相关的模式在激发酰胺I'和II'模式的能量转移机制中起作用。通过求解一个主方程来研究团簇中的能量流动动力学，该主方程将激发系统模式的振动能量弛豫过程描述为一个多步反应，以三阶费米共振参数作为反应速率常数。发现分子内能量转移机制在短时间能量流动动力学中占主导地位，而分子间机制在较长时间内占主导地位。
