Shen Xiao-yan, Liu Jing, Guo Qi-cun, Dai Kang, Shen Yi-fan
School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai 200237, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 May;29(5):1327-30.
A low-power tunable laser was used to populate the Rb(5P(3/2)) hyperfine-structure levels in a pure optically thick vapour in the presence of a dissipative surface. The retrofluorescence intensities and spectrum profile for the 780 nm (5P(3/2)--> 5S(1/2)) and 795 nm (5P(1/2)-->5S(1/2)) lines were measured and analyzed. The glass-vapor interface was considered as two distinct regions, a wavelength-thickness vapor layer adjacent to the surface and a more remote vapor region The first region was analyzed as a spectral filter that annihilated the absorbed photons and the second one as a rich spectral light source. The authors discussed two possible mechanisms for the 5P(1/2) population in the cell [i.e., mechanism(1): collisions Rb(5P(3/2))+Rb(5S(1/2))-->Rb(5P(1/2))+Rb(5S(1/2)); mechanism(2): collisions Rb(5D)+Rb(5S)-->Rb(5P)+Rb(5P)]. For each one of the possible mechanisms considered, the authors gave the theoretical formulation of the retrofluorescence integrated signal associated with 795 nm(5P(1/2)-->5S(1/2)), which was compared with experiment. Two important characteristic aspects of retrofluorescence spectra must be taken into account when dealing with retrofluorescence signals for atomic process investigation: the retrofluorescence intensity dependence on laser power and sensitized laser retrofluorescence line shapes. When the laser frequency is scanned through the hyperfine resonance line, the sensitized retrofluorescence spectra signal corresponding to the 795 nm line has a profile similar to the profile of the retrofluorescence signal at the 780 nm. The authors have pointed out that mechanism(1) gives the linear dependence of the trtrofluorescence as a function of laser power and the spectrum profile. The population of the 5P(1/2) atomic level in an optically thick vapour can be principally explained by the fine-structure excitation transfer process [mechanism(1)]. It appears from our experimental and theoretical investigations that, the spectral properties of the laser-induced Rb 795 nm sensitized retrofluorescence in a pure optically thick vapour near a dissipative surface cannot be explained by the mechanism(2).
在存在耗散表面的情况下，使用低功率可调谐激光器使纯光学厚蒸汽中的铷（Rb(5P(3/2))）超精细结构能级布居。测量并分析了780纳米（5P(3/2)-->5S(1/2)）和795纳米（5P(1/2)-->5S(1/2)）谱线的后向荧光强度和光谱轮廓。玻璃 - 蒸汽界面被视为两个不同区域，一个是与表面相邻的波长 - 厚度蒸汽层，另一个是更远处的蒸汽区域。第一个区域被分析为一个湮灭吸收光子的光谱滤波器，第二个区域被分析为一个丰富的光谱光源。作者讨论了细胞中5P(1/2)布居的两种可能机制[即机制(1)：碰撞Rb(5P(3/2)) + Rb(5S(1/2)) --> Rb(5P(1/2)) + Rb(5S(1/2))；机制(2)：碰撞Rb(5D) + Rb(5S) --> Rb(5P) + Rb(5P)]。对于所考虑的每一种可能机制，作者给出了与795纳米（5P(1/2)-->5S(1/2)）相关的后向荧光积分信号的理论公式，并与实验进行了比较。在处理用于原子过程研究的后向荧光信号时，必须考虑后向荧光光谱的两个重要特征方面：后向荧光强度对激光功率的依赖性和敏化激光后向荧光线形。当激光频率扫过超精细共振线时，对应于795纳米谱线的敏化后向荧光光谱信号的轮廓与780纳米处的后向荧光信号轮廓相似。作者指出，机制(1)给出了后向荧光随激光功率和光谱轮廓的线性依赖性。光学厚蒸汽中5P(1/2)原子能级的布居主要可以通过精细结构激发转移过程[机制(1)]来解释。从我们的实验和理论研究来看，在耗散表面附近的纯光学厚蒸汽中，激光诱导的铷795纳米敏化后向荧光的光谱特性无法用机制(2)来解释。
