用光学-光学双共振光谱技术研究Cs蒸气中的共振交换碰撞

利用窄带半导体激光器泵浦所有具有相同z分量速度的基态Cs原子至激发态，研究了Cs(6P_3/2, v) +Cs(6S_1/2, v′)→Cs(6S_1/2, v) +Cs(6P_3/2, v′)的共振交换碰撞过程。与泵浦光反向平行的另一单模激光器激发6P_3/2至8S_1/2态，以检测6P_3/2态原子的速度分布，确定激发态原子的热能化效应。通过测量8S_1/2→6P_1/2荧光的尖峰强度与相应的多普勒背景的强度比，得到共振交换碰撞速率系数为k=9.62×10-7 cm3·s-1。证明了在纯碱金属蒸气中，由共振交换机制产生的热能化效应的大小比由速度改变碰撞引起的大3个数量级。

Study of Resonance Exchange Collisions in Cesium Vapour by Optical-Optical Double Resonance Spectroscopy

An experimental study of cesium resonance exchange collision, Cs(6P(3/2), v) + Cs(6S(1/2), v')-->Cs(6S(1/2), v) + Cs (6P(3/2), v'), was carried out. Populations of excited atoms that all have the same z component of velocity were produced by pumping a vapor with a narrow-band laser. A counterpropagating single-mode diode laser was used to probe the excited atom velocity distribution in the 6P(3/2)-->8S(1/2) transition. Fluorescence was monitored in the 8S(1/2)-->6P(3/2) transition. The magnitude of the thermalizinng effect of resonance exchange collisions was estimated by measuring the ratio of the intensity in the narrow features to that associated with the Doppler pedestals. The rate coefficient of 9.62 x 10(-7) cm3 x s(-1) for the resonance exchange collisions was yielded. This work demonstrates that, in a pure metal vapor, the thermalization of velocity-selected excited-atom distribution by the mechanism of resonance exchange can be three orders of magnitude greater than that from velocity-changing collisions.