Graduate School of Science, Kobe University, Nada, Kobe 657-8501, Japan.
J Chem Phys. 2010 Jul 7;133(1):014505. doi: 10.1063/1.3428672.
We have studied the temperature dependence of the vibrational frequency fluctuation of the antisymmetric stretching mode of N(3) (-) in D(2)O by three-pulse infrared (IR) photon echo experiments. IR pump-probe measurements were also carried out to investigate the population relaxation and the orientational relaxation of the same band. It was found that the time-correlation function (TCF) of the frequency fluctuation of this mode is well described by a biexponential function with a quasistatic term. The faster decay component has a time constant of about 0.1 ps, and the slower component varies from 1.4 to 1.1 ps in the temperature range from 283 to 353 K. This result indicates that liquid dynamics related to the frequency fluctuation are not highly sensitive to temperature. We discuss the relationship between the temperature dependence of the vibrational frequency fluctuation and that of the molecular motion of the system to investigate the molecular origin of the frequency fluctuation of the solute. We compare the temperature dependence of the frequency fluctuation with that of other dynamics such as dielectric relaxation of water. In contrast to the Debye dielectric relaxation time of D(2)O, the two time constants of the TCF of the frequency fluctuation do not exhibit strong temperature dependence. We propose a simple theoretical model for the frequency fluctuation in solutions based on perturbation theory and the dipole-dipole interaction between the vibrational mode of the solute and the solvent molecules. This model suggests that the neighboring solvent molecules in the vicinity of the solute play an important role in the frequency fluctuation. We suggest that the picosecond component of the frequency fluctuation results from structural fluctuation of the hydrogen-bonding network in water.
我们通过三脉冲红外（IR）光子回波实验研究了 N(3)（-）在 D(2)O 中的反对称伸缩模式振动频率波动随温度的变化。还进行了 IR 泵浦-探针测量，以研究相同带的粒子数弛豫和取向弛豫。结果表明，该模式的频率波动的时间相关函数（TCF）可以很好地用双指数函数来描述，其中包含准静态项。较快的衰减分量的时间常数约为 0.1 ps，而较慢的分量在 283 至 353 K 的温度范围内从 1.4 到 1.1 ps 变化。这一结果表明，与频率波动相关的液体动力学对温度的变化不敏感。我们讨论了振动频率波动的温度依赖性与系统分子运动的关系，以研究溶质的频率波动的分子起源。我们将频率波动的温度依赖性与水的介电弛豫等其他动力学的温度依赖性进行了比较。与 D(2)O 的德拜介电弛豫时间相比，频率波动 TCF 的两个时间常数没有表现出强烈的温度依赖性。我们提出了一个基于微扰理论和溶质振动模式与溶剂分子之间的偶极-偶极相互作用的溶液中频率波动的简单理论模型。该模型表明，溶质附近的相邻溶剂分子在频率波动中起着重要作用。我们认为，频率波动的皮秒分量来自水中氢键网络的结构波动。
