266nm激光光解CHBr_3产生CH(A,B,C)自由基的研究

The Mechanism of 266nm Laser Photodissociation of CHBr_3 to Produce Electronically Excited CH Radical

本文报道用四倍频YAG激光光解CHBr_3分子产生电子激发态的CH自由基,测定了CH(A,B→X)的荧光色散谱,CH(A→X)的时间分辨谱以及CH(A→X)发射光强和激光功率的关系。提出该光解过程可能为CHBr_3连续吸收三个单光子(即“1+1+1”)的激发过程的光解机理。通过测量相对于光解激光不同延时时间的CH(A,B→X)的荧光色散谱,获得了新生成的CH(A)自由基转动驰豫信息。结果表明,在本实验条件下(总压26.5Torr),在100ns以内,转动驰豫过程接近完成。

The electronically excited CH radicals were produced by photodissociation of CHBr_3 molecule using quadrupoled YAG laser. The dispersion spectroscopy of CH(A,B→X), the time-resolved spectroscopy of CH(A→X) at 4315(?), the dependence of the signal intensity of CH(A→X) at 4315(?) on energy density of laser were measured. According to these measurements, the mechanism of the photodissociation of CHBr_3 molecule is proposed. CHBr_3 molecule absorbs continuously three single 266nm photons (i.e. 1+1+1 photon absorption process). By measuring the dispersion spectroscopies of CH(A→X) at different delay time refer to laser firing time, the rotational relaxation process of CH(A) radical was investigated. It is found that the rotational relaxation of CH(A) is nearly finished in present experimental conditions, i.e. 26.6 Torr of total pressure of Ar and 15 mToor of CHBr_3 within 100 ns duration.