飞秒泵浦-探测质谱方法研究苯内转换动力学

摘要

以飞秒400及266 nm激光脉冲结合泵浦-探测飞行时间质谱方法研究了苯S2态内转换动力学. 400 nm双光子过程将苯分子激发到S2电子态,布居在S2电子态的分子由于能级耦合无辐射弛豫到S1电子态. 通过测定C6H6+讯号强度随泵浦-探测延迟时间的改变,获得苯S2及S1电子态的衰减寿命分别为(48±1)fs及(6.5±0.2)ps, S2态及S1电子态的消激发机理被认为是相应势能面间的锥形交叉引起的内转换.%The detection of benzene photoions in pump-probe experiments with the femtosecond laser pulse at 400 and 266 nm has allowed to study the dynamics of the internal conversion after excitation to the electronic S2 state. For the S2 state, an extremely short lifetime τD1=(48±1)fs has been obtained, whereas the lifetime τD2=(6.5±0.2)ps of the S1 state populated by the internal conversion from the S2 state is longer than that of the S2 state. The deactivation of the S2 state as well as the S1 state has been explained by the internal conversion to lower electronic states caused by the conical intersection of the corresponding potential surfaces.