532 nm激光作用下CH3I分子的多光子电离

利用飞行时间质谱仪在超声射流冷却条件下探讨了532 nm激光作用下CH3I分子的多光子电离(MPI)解离过程和机制,得到了分子的飞行时间质谱,质谱中包含较强的I 、CH3 离子信号和较弱的CH3I 、CHn (n≤2)、C 、H 离子信号.不同激光能量下的质谱信号在排布上相似,但在强度上有差别.在532 nm激光作用下CH3I分子的多光子电离包括两个过程:一是CH3I分子由双光子激发到A带解离,生成I原子和CH3基团,然后再吸收光子实现中性碎片电离;另一通道是CH3I分子由三光子共振激发到里德堡C态,处于激发态的母体分子继续吸收两个光子电离形成母体离子,碎片离子可由母体离子解离形成.

Multiphoton ionization of CH3I in the wavelength of 532 nm

The processes and mechanism of multiphoton ionization (MPI) and dissociation of CH3I have been discussed under supersonic beam conditions at 532 nm by using time-of-flight mass spectrometer.The MPI mass spectrum consists of strong signals of I+ and CH3+,together with weak signals of CH3I+,CHn+(n≤2),C+ and H+.There is no change of the alignment of the spectra at different laser energies.The processes of ionization of CH3I include two different excitation pathways at 532 nm.One way is that CH3I molecule is two-photon resonantly excited to A-band and then goes through dissociation to form CH3 and I fragments.Fragments ions are produced by ionization neutral fragments;the other process is that CH3I molecule is three-photon resonantly excited to Rydberg state,and then ionized through additional two-photon absorption to form CH3I+.In succession,a part of parent ions dissociate to produce fragment ions.