Xing Xiao-Peng, Wang Xue-Bin, Wang Lai-Sheng
Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99354, USA.
J Chem Phys. 2009 Feb 21;130(7):074301. doi: 10.1063/1.3077230.
Multiply charged anions possess strong intramolecular Coulomb repulsion (ICR), which has been shown to dictate photoelectron angular distributions (PADs) using photoelectron imaging. Here we report the effects of photoelectron kinetic energies on the PADs of multiply charged anions. Photoelectron images on a series of dicarboxylate dianions, (-)O(2)C(CH(2))(n)CO(2) (-) (D(n) (2-), n=3-11) have been measured at two photon energies, 532 and 266 nm. The first photoemission band of D(n) (2-), which is a perpendicular transition in the absence of the ICR, comes from electron detachment of an O lone pair orbital on the -CO(2) (-) end groups. Recent photoelectron imaging studies at 355 nm show that the PADs of D(n) (2-) peak in the directions parallel to the laser polarization for small n due to the ICR, which directs the outgoing electrons along the molecular axis. The current data show much stronger parallel peaking at 532 nm, but much weaker parallel peaking in the 266 nm data, relative to the 355 nm data. These observations indicate that the ICR has greater influence on the trajectories of slow photoelectrons and much reduced effects on faster photoelectrons. This study demonstrates that the PADs of multiply charged anions depend on the interplay between ICR and the outgoing photoelectron kinetic energies.
多电荷阴离子具有很强的分子内库仑排斥力（ICR），利用光电子成像技术已表明这种排斥力决定了光电子角分布（PADs）。在此我们报告光电子动能对多电荷阴离子PADs的影响。在532和266 nm这两种光子能量下，测量了一系列二羧酸二价阴离子(-)O(2)C(CH(2))(n)CO(2) (-)（D(n) (2-), n = 3 - 11）的光电子图像。D(n) (2-)的第一个光发射带在不存在ICR时是垂直跃迁，它来自-CO(2) (-)端基上O孤对轨道的电子脱离。最近在355 nm进行的光电子成像研究表明，由于ICR，对于小的n值，D(n) (2-)的PADs在平行于激光偏振的方向上出现峰值，这使得出射电子沿着分子轴方向。当前数据显示，相对于355 nm数据，在532 nm时平行峰值要强得多，而在266 nm数据中平行峰值要弱得多。这些观察结果表明，ICR对慢光电子的轨迹影响更大，而对快光电子的影响则大大减小。这项研究表明，多电荷阴离子的PADs取决于ICR和出射光电子动能之间的相互作用。
