Cs(6D_J)+(H_2,H_e)的反应与非反应碰撞能量转移

Reactive and Nonreactive Energy Transfer in Cs(6D_J)+(H_2,H_e) Collisions

在样品池条件下,利用原子荧光光谱方法,测量了Cs(6DJ)与H2,He碰撞中的反应与非反应能量转移截面。利用脉冲激光886nm线双光子激发Cs(6S)到Cs(6D3/2)态,原子荧光中除含有6D3/2→6P的直接荧光外,还含有6D5/2→6P的转移荧光。利用三能级模型的速率方程分析,在不同的He和H2密度下,分别测量直接荧光与转移荧光的时间积分荧光强度比,得到了6D3/2与H2和He碰撞的精细结构转移截面分别为σ=(55±13)×10-16和(16±4)×10-16cm2,同时确定了6D5/2与H2和He的碰撞猝灭速率系数。6D5/2态与H2的碰撞猝灭速率系数比6D5/2与He的大,它是反应与非反应速率系数之和,利用实验数据确定非反应速率系数为6.3×10-10cm3.s-1,得到6D5/2与H2的反应截面为(2.0±0.8)×10-16cm2。利用不同H2(或He)密度下6D5/2→6P3/2时间积分荧光强度,得到6D3/2与H2反应截面为(4.0±1.6)×10-16cm2,6D3/2与H2反应的活性大于6D5/2。

Cs vapor, mixed with a gas was irradiated in a glass fluorescence cell with pulses of 886nm radiation from a YAG-laser-pumped OPO laser, populating 6D3/2 state by two-photon absorption. Cross sections for 6D3/2→6D5/2 transition induced by collisions with various He atoms and Hz molecules were determined using methods of atomic fluorescence. The resulting fluorescence included a direct component emitted in the decay of the optically excited state and a sensitized component arising from the collisionally populated state. At the different densities, we have measured the relative time-integrated intensities of the components and fitted a three-state rate equation model to obtain the cross sections for 6D3/2→6D5/2 transfer： σ= （55±13） ×10^-16 and （16±4） ×10^-16 cm^2 for Hz and He, respectively. The cross sections for the effective quenching of the 6D5/2 state were also determined. The total transfer rate coefficients from the 6D5/2 state for He is small [1. 2 × 10^-10 cm^3.s^-1 ]. The total quenching rate coefficient of the 6D5/2 state is larger for H2[6. 7 × 10-^10 cm^3.s^-1]. For H2 case, the quenching rate coefficient corresponds to reaction and nonreactive energy transfer. Evidence suggests that the nonreactive energy transfer rate coefficient is [6. 3 ×10^-10 cm^3.s^-13. He nce the authors estimated the cross section （2. 0±0. 8）× 10^-16 cm^2 for reactive process Cs（6D5/2）＋H2→CsH＋H. Using the dependence on the pressure of H2 （or He ）of the integrated fluorescence monitored at the 6D5/2→6P3/2 transition the cross section （4. 0±1.6） × 10^-16 cm^2 for Cs （ 6D3/2 ） ＋ H2 →CsH ＋ H was obtained. Thus, the relative reactivity with H2 follows an order of Cs（6D3/2）〉Cs（6D5/2）.