Zhao Yi-kun, Cui Xiu-hua, Bai Zhen-ao, Dai Kang, Shen Yi-fan
School of Physics Science and Technology, Xinjiang University, Urumqi 830046, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 May;29(5):1172-5.
The Rb(5Dj )+H2-->RbH[X 1sigma+(v"==0)]+H photochemical reaction was studied in a cell experiment applying a laser pump-absorption technique. Using two-photon excitation of the Rb5 (2)D atomic level in a Rb-H2 vapor mixture, the resulting fluorescence includes a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state. The RbH molecules are formed in three-body reactive collisions between excited Rb5 (2)D atoms and ground state H2 molecules. Near-infrared absorption band RbH X (1)sigma+ (v"==0-->v'==17) near 852 nm by using a diode laser was measured. The absorbed intensity of laser beam through a length L of the RbH vapor is defined as deltaI' and deltaI" where deltaI' and deltaI" are the absorbed intensity of pumping 5D(3/2) and 5D(5/2) levels, respectively. The ratio of deltaI' to deltaI" contains information on reactivity. w5D(3/2) and W5D(3/2) are the production rates of Rb in the 5D(5/2) and 5D(3/2) levels by direct laser excitation from the 5S(1/2) level. Using a second experiment in which pump laser is used to pump the 5D(3/2) and 5D(5/2) states in a pure Rb vapor (T = 290 K), and the i'/i" where i' and i" are measured intensities of the 5D(3/2)-->5P(1/2) and 5D(5/2)-->5P(3/2) transition, respectively, is determined. At low density of Rb atoms, the 5D mixing rate is neglect. The rate of 5D(3/2) and 5D(5/2) fluorescence yields the ratio of 5D(3/2) to 5D(5/2) pump production rate. The rate equations were solved, and the authors estimate the value of the cross section at T=385 K and P(H2) =400 Pa for collisional energy transfer from Rb5D(3/2) to 5D(5/2), from Rb(5D)to Rb states other than Rb(5D)to be 9.8 x 10(-16) cm2 and 2.0 x 10(-16) cm2, respectively. The reaction cross sections [i.e., Rb(5Dj)+H2-->RbH+H] for j being 3/2 and 5/2 are 5.4 x 10(-7) and 2.3 x 10(-17) cm2, respectively. The relative reactivity with H2 for two studied atoms is in an order of Rb(5D(3/2)>Rb(5D(5/2)), and this is consistent with the result obtained from a laser pump-probe technique.
采用激光泵浦 - 吸收技术在细胞实验中研究了Rb(5Dj)+H2→RbH[X 1σ+(v" = 0)]+H光化学反应。在Rb - H2混合蒸汽中利用Rb5 (2)D原子能级的双光子激发，产生的荧光包括来自光激发态的直接成分和由于碰撞填充精细结构态产生的敏化成分。RbH分子在激发态Rb5 (2)D原子与基态H2分子之间的三体反应碰撞中形成。使用二极管激光器测量了852 nm附近的近红外吸收带RbH X (1)σ+(v" = 0→v' = 17)。通过长度为L的RbH蒸汽的激光束吸收强度定义为ΔI'和ΔI"，其中ΔI'和ΔI"分别是泵浦5D(3/2)和5D(5/2)能级的吸收强度。ΔI'与ΔI"的比值包含反应性信息。w5D(3/2)和W5D(3/2)分别是通过从5S(1/2)能级直接激光激发在5D(5/2)和5D(3/2)能级中Rb的产生率。在第二个实验中，使用泵浦激光器在纯Rb蒸汽（T = 290 K）中泵浦5D(3/2)和5D(5/2)态，并确定i'/i"，其中i'和i"分别是5D(3/2)→5P(1/2)和5D(5/2)→5P(3/2)跃迁的测量强度。在低Rb原子密度下，5D混合率可忽略不计。5D(3/2)和5D(5/2)荧光速率给出了5D(3/2)与5D(5/2)泵浦产生率的比值。求解了速率方程，作者估计在T = 385 K和P(H2)=400 Pa时，从Rb5D(3/2)到5D(5/2)以及从Rb(5D)到除Rb(5D)之外的Rb态的碰撞能量转移截面值分别为9.8×10(-16) cm2和2.0×10(-16) cm2。对于j为3/2和5/2的反应截面[即Rb(5Dj)+H2→RbH + H]分别为5.4×10(-17)和2.3×10(-17) cm2。所研究两种原子与H2的相对反应性顺序为Rb(5D(3/2)>Rb(5D(5/2))，这与激光泵浦 - 探测技术获得的结果一致。
