物理化学学报 >> 2010, Vol. 26 >> Issue (07): 1903-1908.doi: 10.3866/PKU.WHXB20100630

光化学与光谱 上一篇    下一篇

n-C3H7Ii-C3H7I在266 nm的光解: 烷基自由基分支化对C—I解离动力学的影响

张锋, 王艳梅, 张冰, 冯文林   

  1. 重庆理工大学光电信息学院, 重庆 400051
    中国科学院武汉物理与数学研究所, 波谱与原子分子物理国家重点实验室, 武汉 430071
    中国科学院研究生院, 北京 100049
  • 收稿日期:2010-03-02 修回日期:2010-04-05 发布日期:2010-07-02
  • 通讯作者: 张冰 E-mail:bzhang@wipm.ac.cn

Photolysis of n-C3H7I and i-C3H7I at 266 nm: Effect of Alkyl Radical Branching on the Dissociation Dynamics of the C—I Bond

ZHANG Feng, WANG Yan-Mei, ZHANG Bing, FENG Wen-Lin   

  1. School of Optoelectronic Information, Chongqing University of Technology, Chongqing 400051, P. R. China
    State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, P. R. China
    Graduate University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2010-03-02 Revised:2010-04-05 Published:2010-07-02
  • Contact: ZHANG Bing E-mail:bzhang@wipm.ac.cn

摘要:

结合共振增强多光子电离(REMPI)方案, 利用离子影像技术研究了n-C3H7I和i-C3H7I分子的光解动力学. 分析和比较了它们光解过程中所涉及的能量分配和解离态间的非绝热跃迁信息. 它们的I(2P3/2)产物通道的内能所占百分比要大于I*(2P1/2)产物通道的. 随着烷烃自由基变得更加的分支化, 一方面, 原子碎片(I 和I*)的能量分布明显变宽, 暗示了α-碳原子上的烷基具有更复杂的振转模式; 另一方面, 在266 nm光子的泵浦下, 尽管两分子3Q0←X跃迁的谐振强度表现出很小的差别, 但是, 产生I*碎片的几率明显降低, 从n-C3H7I的0.72降到i-C3H7I的0.46. 这可以归因于在光解i-C3H7I过程中弯曲振动模式对产生I和I*的贡献要比n-C3H7I光解过程中弯曲振动模式对I和I*的贡献更明显, 使得3Q0与1Q1态之间的非绝热跃迁得到增强. 此外, n-C3H7I 和i-C3H7I的3Q0←X跃迁并不完全是平行跃迁,对应的跃迁偶极矩与键轴间的夹角分别约为15°和18°.

关键词: 光解动力学, n-C3H7I, i-C3H7I, 离子影像

Abstract:

Photodissociation dynamics of n-C3H7I and i-C3H7I at 266 nm were investigated using an ion imaging technique combined with resonance enhanced multiphoton ionization (REMPI). Information on energy disposal and a nonadiabatic transition between the dissociative electronic states involved in the photodissociation of both molecules were analyzed and compared. The fraction of internal energy in the I channel is greater than that in the I* channel for both molecules. As the alkyl group becomes more branched the energy distribution of the atom fragments (I and I*) becomes obviously wider suggesting that the alkyl radical at the α-carbon atomhas more complicated models of the ro-vibration models. On the other hand, the relative oscillator strengths of these molecules that were pumped using 266 nm photons show a small difference in the 3Q0←X transition. The probability of yielding an I* fragment decreases markedly from 0.72 for n-C3H7I to 0.46 for i-C3H7I. This is attributed to the greater contribution of the bending modes for I and I* during the photodissociation of i-C3H7I than that of n-C3H7I leading to an enhancement of the nonadiabatic transition between the 3Q0 and 1Q1 states. Additionally, the 3Q0←X transition is not a completely parallel transition for both molecules and the angle between the transition dipole moment and the bond axis is estimated to be about 15° for n-C3H7I and 18° for i-C3H7I, respectively.

Key words: Photodissociation dynamics, n-C3H7I, i-C3H7I, Ion imaging

MSC2000: 

  • O644