Itakura Ryuji, Liu Peng, Furukawa Yusuke, Okino Tomoya, Yamanouchi Kaoru, Nakano Hidetoshi
Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Chem Phys. 2007 Sep 14;127(10):104306. doi: 10.1063/1.2768958.
Two-body Coulomb explosion with the C-O bond breaking of methanol induced by intense laser pulses with the duration of Delta t=7 and 21 fs is investigated by the coincidence momentum imaging method. When Delta t=7 fs, the angular distribution of recoil vectors of the fragment ions for the direct C-O bond breaking pathway, CH(3)OH(2+)-->CH(3) (+)+OH(+), exhibits a peak deflected from the laser polarization direction by 30 degrees -45 degrees , and the corresponding angular distribution for the migration pathway, CH(2)OH(2) (+)-->CH(2) (+)+H(2)O(+), in which one hydrogen migrates from the carbon site to the oxygen site prior to the C-O bond breaking, exhibits almost the same profile. When the laser pulse duration is stretched to Delta t=21 fs, the angular distributions for the direct and migration pathways exhibit a broad peak along the laser polarization direction probably due to the dynamical alignment and/or the change in the double ionization mechanism; that is, from the nonsequential double ionization to the sequential double ionization. However, the extent of the anisotropy in the migration pathway is smaller than that in the direct pathway, exhibiting a substantial effect of hydrogen atom migration in the dissociative ionization of methanol interacting with the linearly polarized intense laser field.
采用符合动量成像方法研究了持续时间Δt = 7 fs和21 fs的强激光脉冲诱导甲醇C - O键断裂的两体库仑爆炸。当Δt = 7 fs时，直接C - O键断裂途径CH(3)OH(2+)→CH(3)(+) + OH(+)的碎片离子反冲矢量的角分布呈现出一个从激光偏振方向偏转30度 - 45度的峰值，而迁移途径CH(2)OH(2)(+)→CH(2)(+) + H(2)O(+)（其中一个氢在C - O键断裂之前从碳位点迁移到氧位点）的相应角分布呈现出几乎相同的轮廓。当激光脉冲持续时间延长到Δt = 21 fs时，直接途径和迁移途径的角分布沿激光偏振方向呈现出一个宽峰，这可能是由于动力学取向和/或双电离机制的变化；即从非顺序双电离到顺序双电离。然而，迁移途径中的各向异性程度小于直接途径中的各向异性程度，这表明在与线偏振强激光场相互作用的甲醇解离电离中，氢原子迁移具有显著影响。
