| Budget Amount *help |
¥15,100,000 (Direct Cost: ¥15,100,000)
Fiscal Year 2006: ¥5,200,000 (Direct Cost: ¥5,200,000)
Fiscal Year 2005: ¥9,900,000 (Direct Cost: ¥9,900,000)
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| Research Abstract |
Photofragment angular and energy distributions have been extensively examined in the gas phase photodissociation studies on various molecules because of their importance to obtain dynamical information. In this study, we have systematically examined time-of-flight (TOF) profiles of fragment ions for Mg^+-XCH_3(X=F,Cl,Br, and I) and discussed the product energy distributions as well as the angular distributions to get further information on the photodissociation dynamics of these complexes.
In the photodissociation of Mg^+-ICH_3,five kinds of ions, CH_3^+,Mg^+,I^+,ICH_3^+,and MgI^+ were observed as fragment ions. Among these ions, anisotropic distributions were observed in the TOF profiles of ICH_3^+ and MgI^+ whereas other ions had isotropic distributions. For Mg^+-FCH_3,fragment ions of CH_3^+,Mg^+ and MgF^+ were observed and these ions also showed spatial anisotropy except for mg+. Observed features in the TOF spectra could be qualitatively explained by local excitations of the Mg^+ i
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on (3P_z←3s electron excitation, transition moment vector p is parallel to an Mg-X bond axis) and geometrical structures of the parent complexes. Anisotropy parameters of ICH_3^+ and MgI^+ were determined to be +1.30 and -0.50, respectively, which were 〜60% of the values expected by geometries of the parent ions neglecting rotations of the complex. On the other hand, those of CH_3^+ and MgF^+ formed from Mg^+-FCH_3 were +0.75 for both ions (<40 % of the expected values). In addition, kinetic energy release distributions were also determined for these systems. For iodide system, more than 40 % of available energy was found to be partitioned into translational energy for both ICH_3^+ and MgI^+ ions, whereas energy transfer for fluoride system was about 16 %. From estimations by using statistical or nonstatistical models, nonstatistical processes were more important in the dissociation to produce ICH_3^+ and MgI^+ than the CH_3^+ and MgI^+ formation. This means that the rapid dissociations compared with the rotational period of the parent complex would occur in the iodide system which is consistent with the consideration from the potential energy surfaces. Less
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