激发态Cs(5D)原子间碰撞能量转移

Energy transfer in collisions between two Cs(5D) atoms

用激光二步激发Cs原子至8S态,从谱线的波长及强度可以确定Cs原子的辐射及碰撞过程,5D态主要是由8S→7P→5D跃迁布居的.在1016-1017Cs密度范围内,测量了碰撞能量合并5D+5D→nL+6S(nL=9D,11S,7F)速率系数,因5D→6P(3.0-3.6μm)处于红外本实验不能探测,利用一个已经测量过的过程(即6P+5D→6S+7D)作相对测量,对于9D,11S和7F态,其平均速率系数分别为(8.4±4.2)×10-10,(7.3±3.6)×10-10和(9.7±4.8)×10-10cm3s-1.讨论了碰撞转移过程11S+6S 7F+6S对速率系数的影响.

Using stepwise excitation of the cesium 8S atoms level in Cs vapor, several collisional and radiative processes have been identified from the intensities and spectra of the Cs fluorescence. The 5D state was populated by 8S→7P→SD transitions. In cesium densities 10^16 - 10^17 cm^-3, the energy pooling collisions 5D ＋ 5D→nL ＋ 6S（ nL = 9D, 11S ,7F are studied. Since the 5D→6P（3.0 - 3.6 μm） fluorescence could not be detected with this experiment, the EP rate coefficients have been measured relative to the known rate coefficient of the collision, i. e., 6P ＋ 5D→6S ＋ 7D. The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode laser beam, tuned to 6P3/2→8S1/2 transition, which could be translated parallel to the pump beam. The excited atom densities are combined with measured fluoreseene ratios to determine cross sections for the cesium energy pooling process. The average values （in units of 10^-10 cm^3s^-1） for nL=9D,11S and 7F are 8.4±4.2,7.3 ±3.6,and 9.7±4.8 ,respectively. Influence on k11S and k7F of the energy transfer process 11S ＋ 6S←→7F ＋ 6S is also dicussed.