Zhang Min, Dai Hai-Lung
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
J Phys Chem A. 2007 Sep 27;111(38):9632-9. doi: 10.1021/jp075142v. Epub 2007 Sep 8.
Collision depopulation cross sections of 13 single, highly vibrationally excited levels with 45,000 cm(-1) energy in the electronic ground state of SO(2) in collision with CO in a supersonic jet have been measured. The measurements for these single highly excited quantum states are conducted through pressure dependence of the decay of the fluorescence quantum beat resulted from their coupling with the rovibronic levels in the optically allowed transitions to the (140), (210), and (132) C(1)B(2) levels. The relaxation cross sections of these highly excited states, each with well-defined energy and symmetry, range from 27 to 187 A(2) with an average of 71 A(2). This average cross section is much larger than the hard sphere cross section of 48 A(2). The relaxation cross section is also found to be larger for the quantum states with a larger matrix element in coupling with the "bright" electronically excited level. Both observations suggest a substantial contribution from long range interactions in collision relaxation of highly excited molecules.
已测量了处于电子基态的SO₂中13个单重、高振动激发能级（能量为45000cm⁻¹）与超音速喷流中的CO发生碰撞时的碰撞布居数减少截面。这些单重高激发量子态的测量是通过它们与光学允许跃迁到(140)、(210)和(132)C¹B²能级的振转电子能级耦合所产生的荧光量子拍衰减的压力依赖性来进行的。这些具有明确能量和对称性的高激发态的弛豫截面范围为27至187 Ų，平均为71 Ų。这个平均截面远大于48 Ų的硬球截面。还发现，与“明亮”电子激发能级耦合时矩阵元较大的量子态的弛豫截面也较大。这两个观察结果都表明，长程相互作用在高激发分子的碰撞弛豫中起了很大作用。
