Cs(8S-4F)-Ar,H_2的碰撞能量转移

Collisional energy transfer in Cs(8S-4F)-Ar,H_2 collisions

利用脉冲激光器双光子激发Cs-H_2(或Ar)样品池中的Cs原子至8S态,研究了Cs(8S)+M→Cs(4F)+M,(M=H_2,Ar)碰撞能量转移和Cs(4F)+H2→CsH+H反应过程,建立了二能级模型的速率方程组.在不同的Ar密度下测量直接8S→6P与敏化4F→5D积分荧光强度比,得到8S→4F转移速率系数5.3×10^(-12)cm^3s^(-1)和4F态的猝灭速率系数4.4×10^(-13)cm^3s^(-1).用相同的方法测得Cs-H_2中8S→4F的转移速率系数为1.0×10^(-9)cm^3s^(-1),而4F态的猝灭速率系数1.3×10^(-10)cm^3s^(-1)比Cs-Ar中大得多,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8.3×10^(-11)cm^3s^(-1),得出Cs(4F)与H2的反应截面为(2.0±0.8)×10^(-16)cm^2.与已有的其它实验结果比较,Cs各激发态与H_2的反应活动性顺序为7P>4F>6D>8S.

A pulsed laser was used to excite the 8S state directly from ground state by two-photon absorption . We have investigated direct collisional energy transfer process Cs(8S) + M→Cs(4F) + M , where M=H_2, Ar,and the Cs(4F) + H_2→ CsH + H reaction under gas cell conditions. The resulting fluorescence included a direct component emitted in the decay of the 8S state and a sensitized component arising from the 4F state. At the different Ar densities,we have measured the relative time-integrated intensities of the components and fit a two-state rate equation model to obtain the rate coefficient (5. 3X 10^(-12)cm^3 s^(-1)) for the 8S→4F transfer and quenching (4. 4 × 10^(-13) cm^3 s^(-1)) of the 4F state. In the H_2 case, the total quenching rate coefficient (1. 3 X 10^(-10) cm^3 s^(-1)) corresponds to reaction and nonreactive energy transfer. Evidence suggests that the nonreactive energy transfer rate coefficient is 8. 3×10^(-11)cm^3 s^(-1). Hence we estimate the cross section (2.0±0. 8) × 10^(-16)cm^2 for reactive process Cs(4F) + H_2 →CsH + H . A comparison with previous results yields that the relative reactivity with H_2 for the studied atoms is in an order of Cs(7P)>Cs(4F)>Cs(6D)>Cs(8S).