Laser Studies of Energy Flow in Polyatomic Molecules

实验物理化学计划支持教授乔治W。 哥伦比亚大学的Flynn在他对碰撞的继续研究中 具有“化学意义”的分子的动力学和松弛 振动能的量。 弗林教授将准备高能量或 使用受激准分子泵浦的染料激光器或光学 参数振荡器，然后监测最终的量子态的 使用IR/维斯吸收或UV的碰撞或反应产物 荧光。 多普勒分辨红外二极管激光光谱将产生 关于产物分子速度的信息。 因此，弗林教授可以 确定的振动，旋转和平移能量的 能量受体（浴）分子。 最终目标是确定 能量传递分布函数P（E，E ′），即，的概率 一个初始能量为E的分子， 跃迁到能量E '，振动能E'-E发生变化。 PI将研究猝灭剂的激发机制 振动“暗”状态，并将测量分布函数， 低温（10 K），以衡量碰撞速度的影响， 在松弛过程中形成络合物。 这项研究的重要性在于，它揭示了机制， 这些分子会解离或分裂，然后再重新组合。 通常我们 假设振动能增益的损失由非常重要的 分子间的强烈碰撞，但这只是粗略的近似 与其他过程相比，例如， 作为能量函数的解离速率是已知的。 分布 弗林教授将获得的功能，当加上良好的理论 计算，应该允许更深入地了解 解离和重组过程对于 燃烧和大气化学。

The Experimental Physical Chemistry Program supports Prof. George W. Flynn of Columbia University in his continuing studies on collision dynamics and relaxation of molecules with `chemically significant` amounts of vibrational energy. Prof. Flynn will prepare high energy or reactive donor molecules using excimer-pumped dye lasers or optical parametric oscillators and then monitor the final quantum state of the collision or reaction products using IR/VIS absorption or UV fluorescence. Doppler-resolved IR diode laser spectroscopy will yield information on the velocity of product molecules. Thus Prof. Flynn can determine the vibrational, rotational and translational energy of the energy acceptor (bath) molecules. The ultimate goal is to determine the energy transfer distribution function P(E,E'), i.e., the probability that a molecule, initially at an energy E, will undergo a collision induced transition to an energy E', with change in vibrational energy of E'-E. The PI will investigate the mechanism for excitation of quencher vibrational 'dark' states and will measure the distribution function at low temperatures (10K) to gauge the effects of collision velocity and complex formation in the relaxation process. The importance of the research is that it sheds light on the mechanism by which molecules dissociate, or break apart, and recombine. Normally, we assume that the loss of gain of vibrational energy is controlled by very strong collisions between molecules, but this is a gross approximation compared to the detail with which other processes, for example, the dissociation rate as a function of energy, are known. The distribution function that Prof. Flynn will obtain, when coupled with good theoretical calculations, should allow a much deeper understanding of the dissociation and recombination processes that are so important to combustion and atmospheric chemistry.