Collisional Energy Conversion Mechanisms in Polyatomic Vapors

实验物理化学项目将支持印第安纳大学布卢明顿分校的Charles S. Parmenter继续他在各种分子中状态分辨能量转移的研究。他的实验要点是使用超音速分子束技术来产生几个非常特殊的旋转状态的分子。然后用激光泵浦将分子激发到第一单重态电子激发态，对非弹性散射填充态的分散荧光检测得到单碰撞能量传递通道的相对截面。过去的研究涉及从稀有气体或双原子分子中散射乙二醛（12种振动模式）。在此资助期内，研究者将扩展他对乙二醛与氦或双原子氢的碰撞的研究。他还将研究相对横截面作为碰撞伙伴之间质心能量的函数。最后，交叉梁实验将扩展到氘化甲醛，由于其非平面激发态，偶极矩的存在和主动振动模式的极端非调和性，这是一个与乙二醛截然不同的分子体系。本研究针对多原子分子内的振动和旋转能流问题。这是分子如何获得反应所需活化能的核心问题。无碰撞振动能量流是高振动激发分子解离或异构化的一个基本方面。

The Experimental Physical Chemistry Program will support Charles S. Parmenter of Indiana University in Bloomington to continue his studies of state-resolved energy transfer in various molecules. The gist of his experiment is to use a supersonic molecular beam technique to generate molecules in a few, very specific rotational states. Laser pumping is then used to excite the molecule to the first singlet electronic excited state, and dispersed fluorescence detection of states populated by inelastic scattering yields relative cross sections for single collision energy transfer channels. Past efforts involved scattering of glyoxal (12 vibrational modes) from rare gases or diatomic molecules. During this funding period, the investigator will extend his studies on glyoxal to collisions with helium or diatomic hydrogen. He will also study relative cross sections as a function of center-of-mass energy between collision partners. Finally, the crossed beam experiments will be extended to deuterated formaldehyde, a molecular system far different from glyoxal due to its nonplanar excited electronic state, presence of a dipole moment and extreme anharmonicity in an active vibrational mode. The research is directed at the problem of vibrational and rotational energy flow within polyatomic molecules. This is central to the problem of how molecules acquire the activation energy needed for reactions. The collision-free vibrational energy flow is a fundamental aspect of dissociation or isomerization of molecules with high vibrational excitation.