通过对CH_3I,C_2H_5I,n-C_3H_7I,iso-C_3H_7I,n-C_4H_9I,t-C_4H_9I以及CH_2ClI在248nm的激光裂解实验研究,进一步论证光解通道比I/I主要受解离动力学过程中~3Q_0和~1Q_1态的位能曲线交叉机理控制,同时讨论不同Taft极化因子的烷基取代基对n→σ跃迁的影响。利用Landau-Zener关系式和Hammett方程,建立了光解通道比与光解碎片能量分配以及Taft因子之间的关系表达式,能合理地解释实验观察的结果。 The experimental results of laser pyrolysis of CH_3I, C_2H_5I, n_C_3H_7I, iso-C_3H_7I, n-C_4H_9I, t-C_4H_9I and CH_2ClI at 248nm further demonstrate that the photolysis channel ratio I / I is mainly affected by ~ 3Q_0 And ~ 1Q_1 state potential energy curve crossing mechanism control, and discusses the different Taft polarization factor alkyl substituents on n → σ transition. The Landau-Zener relationship and the Hammett equation were used to establish the expression of the relationship between the photolysis channel ratio and the photodissociation energy distribution and the Taft factor, which can reasonably explain the experimental observations.