基于飞秒光电子影像技术与飞行时间质谱,对氯丙烯(C3H5Cl)在200、 400、800 nm飞秒脉冲下的光电离/解离机理进行了研究。结果表明:C3H5Cl的光电离/解离机理与激光波长存在依赖关系。 在短波长200 nm, 母体分子C3H5Cl以双光子电离为主要通道,其他的碎片离子则来源于C3H5Cl+的解离;当波长 向长波方向变化,如800 nm时, C3H5Cl中间态的解离开始占主导地位,碎片离子的信号也相应增强。 光电子能谱进一步证实了在400 nm和800 nm存在来源于中性碎片的光电子,这些中性碎片是由C3H5Cl的 中间态直接解离产生的。这意味着在400 nm和800 nm母体分子可能被激发到寿命较短的中间解离态,解离产 生中性碎片,使光解离过程在长波段扮演重要角色。

Based on femtosecond photoeletron imaging technique and time-of-flight mass spectroscopy, the photoionization/photodissociation mechanisms of allyl chloride (C3H5Cl) at 200, 400, 800 nm femtosecond laser pulses are investigated. Results show that the photoionization/photodissociation mechanisms of C3H5Cl have dependence on laser wavelength. At short wavelength 200 nm, two-photon ionization is the dominant channel of parent molecule C3H5Cl, and other fragment ions are generated by dissociation of C3H5Cl+. When it shifts to longer wavelength, such as 800 nm, dissociation from intermediate states of C3H5Cl starts to play a leading role, and the signals of fragment ions are also enhanced. Photoelectron spectra further confirm that there are photoelectrons coming from neutral fragments at 400 nm and 800 nm, and they are generated from dissociation of the intermediate states of C3H5Cl. It implies that at 400 nm and 800 nm, the parent molecule may be excited to intermediate dissociation states with shorter life-time and produce neutral fragments, which makes the process of light dissociation play an important role in the long waveband.