中文摘要：

利用飞秒时间分辨质谱技术研究了邻碘甲苯分子在26612111激发下的光解动力学．光解产物碎片通过800nm强激光场下的多光子电离实现探测．拟合光解产物CTH7自由基和I原子随泵浦一探测延迟时间变化的信号，得到解离时间为380：h50fs，它反映的是266nm同时激发nσ^＊和ππ^＊态后C-I键的平均解离时间．此外，还利用基态碘原子的共振波长298．23nm作为探测光，通过共振增强多光子电离方法对解离生成的基态碘原子进行了选择性探测．拟合I＋随泵浦-探测延迟时间变化的信号，得到解离时间为400±50fs，这与通过800nm多光子电离得到的解离时间一致，表明解离生成的主要产物是基态碘原子．

英文摘要：

The photodissociation dynamics of 2-iodotoluene following excitation at 266 nm have been investigated employing femtosecond time-resolved mass spectrometry. The photofragments are detected by multiphoton ionization using an intense laser field centered at 800 nm. A dissociation time of 3804-50 fs was measured from the rising time of the co-fragments of toluene radical （C7H7） and iodine atom （I）, which is attributed to the averaged time needed for the C-I bond breaking for the simultaneously excited nσ and ππ＊ states by 266 nm pump light. In addition, a probe light centered at 298.23 nm corresponding to resonance wavelength of ground-state iodine atom is used to selectively ionize ground-state iodine atoms generated from the dissociation of initially populated hσ＊ and ππ＊ states. And a rise time of 4004-50 fs is extracted from the fitting of time-dependent I＋ transient, which is in agreement with the dissociation time obtained by multiphoton ionization with 800 nm, suggesting that the main dissociative products are ground-state iodine atoms.