Velasco A M, Lavín C, Dolgounitcheva O, Ortiz J V
Departmento de Química Física, Universidad de Valladolid, 47005 Valladolid, Spain.
Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, USA.
J Chem Phys. 2014 Aug 21;141(7):074308. doi: 10.1063/1.4892584.
Vertical excitation energies of the methyl and silyl radicals were inferred from ab initio electron propagator calculations on the electron affinities of CH3(+) and SiH3(+). Photoionization cross sections and angular distribution of photoelectrons for the outermost orbitals of both CH3 and SiH3 radicals have been obtained with the Molecular Quantum Defect Orbital method. The individual ionization cross sections corresponding to the Rydberg channels to which the excitation of the ground state's outermost electron gives rise are reported. Despite the relevance of methyl radical in atmospheric chemistry and combustion processes, only data for the photon energy range of 10-11 eV seem to be available. Good agreement has been found with experiment for photoionization cross section of this radical. To our knowledge, predictions of the above mentioned photoionization parameters on silyl radical are made here for the first time, and we are not aware of any reported experimental measurements. An analysis of our results reveals the presence of a Cooper minimum in the photoionization of the silyl radical. The adequacy of the two theoretical procedures employed in the present work is discussed.
甲基和甲硅烷基自由基的垂直激发能是通过对CH3(+)和SiH3(+)电子亲和能进行从头算电子传播子计算推断得出的。利用分子量子缺陷轨道方法获得了CH3和SiH3自由基最外层轨道的光电离截面和光电子角分布。报告了与基态最外层电子激发所产生的里德堡通道相对应的各个电离截面。尽管甲基自由基在大气化学和燃烧过程中具有重要意义，但似乎只有10 - 11 eV光子能量范围内的数据可用。该自由基的光电离截面与实验结果吻合良好。据我们所知，本文首次对甲硅烷基自由基上述光电离参数进行了预测，且我们未发现任何已报道的实验测量结果。对我们结果的分析揭示了甲硅烷基自由基光电离过程中存在库珀极小值。讨论了本工作中所采用的两种理论方法的适用性。
