Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy.
Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy.
复制标题
偏振选择性二维红外光谱中重定向引起的光谱扩散的观察和理论。
DOI：
10.1063/1.4920949
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
M. Fayer
中科院分区：
文献类型：
--
作者：
Patrick L Kramer;J. Nishida;Chiara H. Giammanco;Amr Tamimi;M. Fayer
在超快多维红外光谱的几乎所有应用中，光谱自由度（例如，跃迁频率）和跃迁偶极子的方向都被假定为解耦的。我们提出的实验结果证实频率波动可能是由旋转运动引起的，并在适当的条件下观察到。介绍了在各种偏振条件下可观测的频频相关函数 (FFCF) 的理论，并通过模型计算重现了 FFCF 速率的定性趋势。使用偏振选择性二维红外 (2D IR) 光谱确定的 FFCF 是频率-旋转耦合的直接报告。对于室温离子液体中的溶质甲醇，羟基 (O-D) 拉伸的 FFCF 由于光谱扩散而衰减，速率取决于激发脉冲的偏振。 2D IR 振动回波脉冲序列由三个激发脉冲组成，它们生成振动回波，即第四个脉冲。当前两个激励脉冲的偏振垂直于第三个脉冲和回波 <XXY Y> 时，观察到比标准全并行配置 <XXXX> 更快的 FFCF 衰减，其中所有四个脉冲都具有相同的偏振。使用偏振〈XY XY〉（“偏振光栅”配置）的 2D IR 实验给出了比〈XXXX〉配置衰减更慢的 FFCF。散装水的偏振选择性 2D 红外光谱没有表现出偏振相关的 FFCF 衰减；光谱扩散与水系统中的重新定向有效地解耦。
In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, 〈XXY Y〉, than in the standard all parallel configuration, 〈XXXX〉, in which all four pulses have the same polarization. The 2D IR experiment with polarizations 〈XY XY〉 ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the 〈XXXX〉 configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.
DOI：
10.1021/jp046711r
发表时间：
2004-12
期刊：
The journal of physical chemistry. A
影响因子：
--
作者：
T. Steinel;J. Asbury;Junrong Zheng;M. Fayer
通讯作者：
T. Steinel;J. Asbury;Junrong Zheng;M. Fayer