飞秒激光场中氯丙烯的光电离/解离机制研究

利用50fs的激光脉冲对氯丙烯在200nm、400nm和800nm下的光电离/解离机理进行了研究. 实验获得了氯丙烯在三种波长下的电离质谱和光强指数，分析了母体和碎片离子强度随波长的变化关系. 在200nm时，C3H5Cl+来源于飞秒脉冲的直接非共振电离，其它碎片离子均来源于母体离子的电离解离过程；在400nm时，部分分子被激发到高里德堡态从而解离产生C3H5，C3H5再次吸收光子电离导致C3H5+的信号增强；在800nm时，部分分子被同时激发到了排斥态nσ*和多个高里德堡态而发生解离.更多通道产生C3H5使得C3H5+产量进一步增加.由于C3H4+来自C3H5Cl+以及C3H5+的电离解离过程，因此，C3H4+产率随波长变化相对较缓.

Photoionization/photodissociation mechanism of allyl chloride with a femtosecond laser pulse

The photoionization/photodissociation mechanism of allyl chloride has been studied by a 50-fs laser pulse at 200 nm, 400 nm and 800 nm. With the mass spectra and laser power index that record at three different wavelengths, the dependence of quantum yield on the wavelength is analyzed. It is found that the parent ion (C3H5Cl+) comes from directly non-resonance ionization with 200 nm femtosecond pulse, while the daughter ions are from dissociative ionization of C3H5Cl+. At 400 nm, some molecules are excited to the high Rydberg state and C3H5 radicals are generated by direct dissociation. The enhancement of C3H5+ signal is observed since multi-photon ionization of C3H5 increases the population of C3H5+. At 800 nm, nσ* states and some Rydberg states are both populated. The further increased population of C3H5 leading to an increase of C3H5+. On the other hand, the wavelength dependence of C3H4+ yield is less pronounced, since it comes from dissociative ionization of C3H5+ and C3H5Cl+.