Cs-He混合蒸气中的辐射陷获效应和6P3／2能级有效辐射率的测量  

Radiation Trapping Effect and Measurement of the Cs(6P_(3/2)) Level Effective Radiation Rate in the Vapor Mixed with He

作　　者：沈晓燕[1] 戴康[2] 沈异凡[2] 

机构地区：[1]华东理工大学化学与分子工程学院,上海200237 [2]新疆大学物理科学与技术学院,新疆乌鲁木齐830046

出　　处：《光谱学与光谱分析》2008年第7期1464-1467,共4页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(10264004,10664003)资助

摘　　要：测量了Cs-He混合蒸气中Cs（6P3／2）共振能级的有效辐射率，圆柱形样品池充入金属Cs和气压PHe为0-500Pa的He，样品池温度控制在330-370K之间，在池中产生10^12～10^13 cm^-3。的Cs原子密度，使用单模半导体激光器（泵浦激光）将cs原子激发至6P3／2态，另一调谐到6P3／2→8S1／2的单模激光束（检测激光）与泵浦束反平行通过样品池，并在池的直径方向平行移动，通过对检测激光束的吸收测定了激发态原子密度及其空间分布。由于辐射陷获存在，有效辐射率是自然辐射率与透射因子（发射的光子在探测区域内没有被吸收的平均概率，它与吸收截面及激发态原子密度和空间分布有关）的乘积。由6P3／2原子密度及其空间分布结合6P3/2←6S1／2跃迁线的碰撞增宽计算了透射因子，从而得到了不同He气压下，Cs D2线的有效辐射率。从6P3／26→S1/2跃迁线强度I852的测量，得到的不同He气压下有效辐射率的比值与理论计算得到的比值相符。The effective radiation rate for Cs（6P3/2） resonance level in the presence of helium was determined. A cell filled with Cs metal and He at pressure PHe （0-500 Pa） was established at T= 300 K. The cell was heated in the temperature range between 330 and 370 K, which produced Cs number densities approximately in the range between 10^12 and 10^13 cm^-3. Cs atoms were excited to the 6P3/2 state using a single-mode diode laser（pump laser）. The transmission of the medium at the center of the Doppler envelope of the strong h.f. component of the CsD2 line due to hyperfine pumping alone amounts to ≈5%. The assumption that has been made is that the lower-state hyperfine levels are populated in a statistical ratio. The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam （probe laser） tuned to the 6P3/2→8S1/2 transition which could be translated parallel to the pump beam. In the presence of radiation trapping, the spontaneous radiation rate is multiplied by the transmission factor T6P3/2→6S1/2 , which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed. The T6P3/2→6S1/2 is related to the frequency dependent absorption cross section and the density and spatial distribution of atoms at the level of the transition. Position dependent 6P3/2 state densities were combined with the eollisional broadening rate of 6P3/2←6S1/2 line due to the perturbation of both helium and cesium to yield T6P3/2→6S1/2. The effective radiation rates of the Cs D2 line as a function of the He pressure PHe were obtained. The helium caused line broadening and therefore increased the effective radiation rate. The fluorescence intensity I85z of the 6P3/2→6S1/2 emission was measured simultaneously. The measured fluorescence ratios determined the ratios of the effective radiation rates at different He density. These ratios are in agree

关 键 词：激光光谱 有效辐射率 辐射陷获 压力增宽 Cs-He混合蒸气 

分 类 号：O562.3[理学—原子与分子物理]