Brunsvold Amy L, Garton Donna J, Minton Timothy K, Troya Diego, Schatz George C
Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA.
J Chem Phys. 2004 Dec 15;121(23):11702-14. doi: 10.1063/1.1815271.
Crossed molecular beams experiments and classical trajectory calculations have been used to study the dynamics of Ar+ethane collisions at hyperthermal collision energies. Experimental time-of-flight and angular distributions of ethane molecules that scatter into the backward hemisphere (with respect to their original direction in the center-of-mass frame) have been collected. Translational energy distributions, derived from the time-of-flight distributions, reveal that a substantial fraction of the collisions transfer abnormally large amounts of energy to internal excitation of ethane. The flux of the scattered ethane molecules increased only slightly from directly backward scattering to sideways scattering. Theoretical calculations show angular and translational energy distributions which are in reasonable agreement with the experimental results. These calculations have been used to examine the microscopic mechanism for large energy transfer collisions ("supercollisions"). Collinear ("head-on") or perpendicular ("side-on") approaches of Ar to the C-C axis of ethane do not promote energy transfer as much as bent approaches, and collisions in which the H atom is "sandwiched" in a bent Ar...H-C configuration lead to the largest energy transfer. The sensitivity of collisional energy transfer to the intramolecular potential energy of ethane has also been examined.
交叉分子束实验和经典轨迹计算已被用于研究超热碰撞能量下氩气与乙烷碰撞的动力学。已收集了散射到后半球（相对于其在质心坐标系中的原始方向）的乙烷分子的实验飞行时间和角分布。从飞行时间分布得出的平动能量分布表明，相当一部分碰撞将异常大量的能量转移到乙烷的内部激发上。散射的乙烷分子通量从直接向后散射到侧向散射仅略有增加。理论计算显示出与实验结果合理一致的角分布和平动能量分布。这些计算已被用于研究大能量转移碰撞（“超级碰撞”）的微观机制。氩气与乙烷的C-C轴共线（“正面碰撞”）或垂直（“侧面碰撞”）的接近方式促进能量转移的程度不如弯曲接近方式，并且氢原子“夹在”弯曲的Ar...H-C构型中的碰撞导致最大的能量转移。还研究了碰撞能量转移对乙烷分子内势能的敏感性。
