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首页> 外文期刊>The Journal of Chemical Physics >SOLVATION AND SOLVENT EFFECTS ON THE SHORT-TIME PHOTODISSOCIATION DYNAMICS OF CH2I2 FROM RESONANCE RAMAN SPECTROSCOPY
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SOLVATION AND SOLVENT EFFECTS ON THE SHORT-TIME PHOTODISSOCIATION DYNAMICS OF CH2I2 FROM RESONANCE RAMAN SPECTROSCOPY

机译：共振拉曼光谱对CH2I2短时间光解离动力学的溶剂化和溶剂作用

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Resonance Raman spectra of CH2I2 have been obtained at excitation wavelengths of 369, 355, and 342 nm in cyclohexane solution and in methanol solution at excitation wavelengths of 355 acid 342 nm. Resonance Raman spectra were also measured for CH2I2 in the vapor phase with an excitation wavelength of 355 nm. The resonance Raman spectra of CH2I2 exhibit most of:their intensity in fundamentals, overtones, and combination bands of modes nominally assigned as the I-C-I symmetric stretch, the I-C-I bend, and the I-C-I antisymmetric stretch vibrations. The absorption spectra and resonance Raman intensities of the gas phase and methanol solution phase diiodomethane spectra were simulated using a simple model and time-dependent wave packet calculations. Normal mode coefficients from normal coordinate calculations were used to convert the motion of the wave packet on the excited electronic state surface from dimensionless normal coordinates into internal coordinates of the molecule. The short-time photodissociation dynamics of diiodometfi8ne in the vapor phase shows that the two C-I bonds are lengthening by the same amount, the I-C-I angle becomes smaller, the H-C-I angles become larger,and the H-C-H angle becomes smaller. The two C-I bonds appear essentially equivalent in the Franck-Condon region of the gas phase photodissociation which implies that the molecule chooses which C-I bond is broken after the wave packet has left the Franck-Condon region of the potential energy surface. Comparison of the gas phase resonance Raman spectrum with solution phase spectra obtained in cyclohexane and methanol solvents reveals that the short-time photodissociation dynamics are noticeably changed by solvation with a large solvent-induced symmetry breaking observed. In the Franck-Condon region of the solution phase diiodomethane photodissociation in methanol solvent the two C-I bond become larger by differing amounts, the I-C-I angle becomes smaller the H-C-H angle becomes smaller, and the H-C-I angles differ from the corresponding gas phase values. During the initial stages of the solution phase photodissociation (at least in methanol and cyclohexane solvents) the two C-I bonds are not the same and this suggests that the molecule chooses which C-I bond will be broken soon after photoexcitation. (C) 1996 American Institute of Physics. [References: 52]
机译：CH2I2的共振拉曼光谱已在369、355和342 nm的激发波长下在环己烷溶液中和在甲醇溶液中在355酸342 nm的激发波长下获得。还测量了气相中CH2I2的共振拉曼光谱，激发波长为355 nm。 CH2I2的共振拉曼光谱表现出大部分强度：其在基频，泛音和模式组合带中的强度，这些强度标称为I-C-I对称拉伸，I-C-I弯曲和I-C-I反对称拉伸振动。使用简单模型和随时间变化的波包计算，模拟了气相和甲醇溶液相二碘甲烷光谱的吸收光谱和共振拉曼强度。使用来自正态坐标计算的正态模系数将波包在受激电子态表面上的运动从无量纲正态坐标转换为分子的内部坐标。气相中二碘键氟的短时光解离动力学表明，两个C-I键延长相同的量，I-C-I角变小，H-C-I角变大，H-C-H角变小。这两个C-1键在气相光解离的Franck-Condon区域中看起来基本相等，这意味着在波包离开势能表面的Franck-Condon区域之后，分子选择哪个C-1键被断开。气相共振拉曼光谱与在环己烷和甲醇溶剂中获得的溶液相光谱的比较表明，溶剂化可显着改变短时光解离动力学，并且观察到较大的溶剂诱导的对称性破坏。在甲醇溶剂中溶液相二碘甲烷光解的Franck-Condon区中，两个C-I键变大的量不同，I-C-I角变小，H-C-H角变小，并且H-C-I角不同于相应的气相值。在溶液相光解离的初始阶段（至少在甲醇和环己烷溶剂中），两个C-1键不相同，这表明分子选择在光激发后很快会破坏哪个C-1键。 （C）1996年美国物理研究所。 [参考：52]

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