Department of Physics, Stockholm University, S-106 91 Stockholm, Sweden.
J Chem Phys. 2011 Aug 14;135(6):064302. doi: 10.1063/1.3622589.
We report on measurements of the ionization and fragmentation of polycyclic aromatic hydrocarbon (PAH) targets in Xe(20+) + C(16)H(10) and Xe(20+) + C(16)H(10) collisions and compare results for the two C(16)H(10) isomers: pyrene and fluoranthene. For both types of targets, i.e., for single PAH molecules isolated in vacuum or for isomerically pure clusters of one of the molecules, the resulting fragment spectra are surprisingly similar. However, we do observe weak but significant isomer effects. Although these are manifested in very different ways for the monomer and cluster targets, they both have at their roots small differences (<2.5 eV) between the total binding energies of neutral, and singly and multiply charged pyrene and fluoranthene monomers. The results will be discussed in view of the density functional theory calculations of ionization and dissociation energies for fluoranthene and pyrene. A simple classical over-the-barrier model is used to estimate cross sections for single- and multiple-electron transfer between PAHs and ions. Calculated single and multiple ionization energies, and the corresponding model PAH ionization cross sections, are given.
我们报告了在 Xe(20+) + C(16)H(10) 和 Xe(20+) + C(16)H(10) 碰撞中多环芳烃 (PAH) 靶的电离和碎裂的测量结果，并比较了两种 C(16)H(10) 异构体：芘和荧蒽的结果。对于这两种类型的靶标，即真空隔离的单个 PAH 分子或一种分子的同素异形体纯团簇，所得的碎片光谱惊人地相似。然而，我们确实观察到了微弱但显著的异构体效应。尽管这些在单体和团簇靶标中表现出非常不同的方式，但它们都源于中性、单电荷和多电荷芘和荧蒽单体的总结合能之间的微小差异（<2.5 eV）。结果将根据对荧蒽和芘的电离和离解能的密度泛函理论计算进行讨论。简单的经典过垒模型用于估计 PAH 和离子之间的单电子和多电子转移的截面。给出了计算得到的单和多电离能，以及相应的模型 PAH 电离截面。
