弯曲振动对CS_2分子~1B_2(~1Σ_u^+)态预解离寿命的影响

Effect of Vibrational Angular Momentum on the Lifetime of CS_2 ~1B_2(~1Σ_u^+) State

在209.5～216nm,采用光解碎片激发(PHOFEX)谱技术,对CS2分子1B2(1Σ+u)态预解离寿命进行了 考察.测量在超声射流中进行.信号来自解离碎片CS(A1Π,v′=0←X1Σ+,v″=0)Q支带头的激光诱导荧光 (LIF).预解离寿命是通过对谱带进行拟合来提取的.拟合中假定基态转动布居为Boltzmann分布,寿命加宽的转 动谱线为Lorentz线形.通过拟合共获得1B2(1Σ+u)态13个跃迁所对应的预解离寿命,其中6个数据是新得到的. 结果表明,基态振动角动量量子数l或激发态转动角量子数K(K=l)对预解离寿命有明显的影响.对于激发态的 同一振动能级,较大的K对应于较短的预解离寿命.实验中采用可加热的射流喷嘴,用以提高热带激发的强度, 以改善对较大转动角量子数K的影响的考察.

Predissociation lifetimes of totally 13 vibrational levels in the 1B 2 state of jet-cooled CS 2 have been determined by simulating the rotational band contours of the PHOFEX spectrum in the range of 209.5~216 nm, where the PHOFEX spectrum was obtained by monitoring the laser-induced fluorescence of CS fragment via the Q band head excitation of (A 1Π, v′=0)←(X 1Σ +, v″=0) transition. In order to investigate the influence of vibrational angular momentum quantum number K of the excited 1B 2( 1Σ + u) state, the nozzle was heated to increase the hot-band transition intensities. The results indicate that, for levels with the same vibrational quantum number but different K numbers in the 1B 2( 1Σ + u) state of CS 2,the lifetime decreases with the increasing of quantum number K, suggesting that the dissociation could be accelerated by K number.