MOLECULAR ASPECTS OF DYNAMICS IN REACTION PROCESSES AND MOLECULAR INTERACTIONS IN SOLUTION

我们的研究项目的重点是溶液和玻璃中物理和光化学过程的超快光谱研究。为了利用飞秒激光光谱技术研究化学和生物过程中溶质-溶剂相互作用的动力学过程，我们研究了溶剂化、能量弛豫、电子/质子转移以及光解产物间的成对复合等物理化学过程。研制了用于泵浦探测、三脉冲光子回波、克尔门发射、光学克尔和荧光上转换光谱测量的镁橄榄石激光器（26 fs），并对TPM染料进行了时间分辨为30 fs的超快泵浦探测测量。信号以多指数方式衰减，并且较慢的组分比较快的组分对溶剂粘度表现出更强的线性依赖性。活化能和有效值 ...更多信息 对于较慢的衰变来说，体积较大。这一结果可以用溶剂化壳层的时间依赖性粘度或层次结构的影响来解释。利用蓝铜蛋白质，我们研究了蛋白质动力学与光激发和无辐射失活的电荷转移态的超快泵浦-探测光谱。观察到一个相干的低频振动模式，其相位从其他局域拉曼模式的相位移。这种低频模式很可能归因于包含蛋白质骨架运动的离域模式。我们采用参考相互作用位点模型理论来估计溶质-溶剂系统的平均能量的弛豫动力学以及从溶质分子角度看溶剂的随时间变化的径向分布函数。理论计算结果表明，第二溶剂壳层的重排比第一溶剂壳层的重排慢一个数量级。我们认为，进一步的溶剂壳层的缓慢弛豫可以在非均匀谱宽的动态弛豫中发挥重要作用，这在我们之前的时间分辨空穴实验中已经观察到，通过对溶液中成对自由基对的分子动力学模拟，阐明了偶极自由基在非极性和极性溶液中的动力学行为，溶剂.偶极-偶极相互作用使自由基对以小的分离稳定。偶极对可以是实验观察到的夹心自由基二聚体的前体。偶极对的构象可能不利于自由基的复合，这可能是观察到的对氨基苯硫基自由基的高逃逸几率的原因。我们已经展示了二维三脉冲光子回波测量的染料掺杂PMMA在30 K。即使当布居周期T延长到> 100 ps时，重定相和回波形成仍然清晰。结果表明，回波信号本身具有振动结构。少

The focus of our research project is the ultrafast spectroscopic study of photophysical and photochemical processes in solution and glasses. To elucidate the dynamics of the solute-solvent interactions in chemical and biological processes by the femtosecond laser spectroscopy, physico-chemical processes including solvation, energy relaxation, electron/proton transfer, and geminate recombination between photodissociation products are under investigation.Cavity-dumped Kerr-lens mode-locked Ti : sapphire laser(12 fs) and Cr : forsterite laser(26 fs) were developed for the measurements of pump-probe, three-pulse photon echo, Kerr-gate emission, optical Kerr, and fluorescence up-conversion spectroscopy.We have carried out ultrafast pump-probe measurements of TPM dyes with a time resolution of 30 fs. The signal decays in a multiexponential manner, and the slower components showed stronger linear dependence on the solvent viscosity than the faster ones. The activation energies and effective v … More olumes were larger for slower decays. The results can be explained by the effect of the time dependent viscosity or the hierarchy structure of the solvation shell.Using a blue copper protein, we have studied protein dynamics associated with optical excitation and radiationless deactivation of the charge transfer state by an ultrafast pump-probe spectroscopy. A coherent low frequency vibrational mode of which the phase shifted from those of the other localized Raman modes was observed. This low frequency mode most probably can be attributed to the delocalized mode including the protein skeletal motion.We employ a reference interaction-site model theory to estimate the relaxation dynamics of the average energy of solute-solvent systems as well as the time-dependent radial distribution functions of solvents viewed from the solute molecule. The theoretical results indicate that the rearrangement of the second solvent shell is about an order of magnitude slower compared with that of the first shell. We suggest that the slower relaxation of further solvent shells can play a significant role in the dynamic relaxation of the inhomogeneous spectral width, which has been observed in our previous experiment of the time resolved hole-burning and fluorescence spectroscopy.Molecular dynamics simulation of a simple model system of the geminate radical pair in solution has been performed to elucidate the dynamic behavior of the dipole radicals in nonpolar and polar solvents. The dipole-dipole interaction stabilized the radical pair with a small separation. The dipole pair can be the precursor of the experimentally observed sandwich radical dimer. The conformation of the dipole pair may not be favorable for the recombination of the radicals, which can be the reason of the high escape probability observed for the p-aminophenylthiyl radical.We have demonstrated two-dimensional three-pulse photon echo measurement of a dye doped PMMA at 30K. Rephasing and echo formation were still clear even when the population period, T, was extended to > 100 ps. The results indicate that the echo signal itself has the vibrational structure. Less