Radiation Trapping Effect and Measurement of the Cs(6P3/2) Level Effective Radiation Rate in the Vapor Mixed with He
SHEN Xiao-yan1,DAI Kang2,SHEN Yi-fan2*
1. Department of Chemistry, East China University of Science & Technology, Shanghai 200237, China 2. Department of Physics, Xinjiang University, Urumqi 830046, China
Abstract：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 1012 and 1013 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 collisional 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 I852 of the T6P3/2→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 agreement with theoretical evaluation.
沈晓燕1,戴康2,沈异凡2*. 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[J]. 光谱学与光谱分析, 2008, 28(07): 1464-1467.
SHEN Xiao-yan1,DAI Kang2,SHEN Yi-fan2*. Radiation Trapping Effect and Measurement of the Cs(6P3/2) Level Effective Radiation Rate in the Vapor Mixed with He. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2008, 28(07): 1464-1467.
［1］ Vadla C, Horvatic V, Niemax K. Spectrochim. Acta, 2003, B58(7)：1235. ［2］ Correll T L, Horvatic V, Omenetto N, et al. Spectrochim. Acta, 2006, B61：623. ［3］ LI Yuan-yuan, YIN Gui-qin, DAI Kang, et al(李媛媛, 殷桂琴, 戴 康，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2006, 26(9)：1624. ［4］ Jabbour Z J, Namiotka R K, Huennehens J, et al. Phys. Rev., 1996, A54(2)：1372. ［5］ Namiotka R K, Huennehens J, Allegrini M. Phy. Rev.，1997, A56(1)：514. ［6］ Movre M, Vadla C, Horvatic V. J. Phys. B-At. Mol. Opt. Phys., 2000, 33：3001. ［7］ WANG Shu-ying, SUN Mao-zhu, DAI Kang, et al(王淑英，孙茂珠，戴 康，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析),2007，27(6)：1044. ［8］ Jabbour Z J, Sagle J, Namiotha R K, et al. J. Quant. Spectrosc. Radiat Transfer，1995, 54(5)：767. ［9］ Lewis E. Phys. Rep., 1980, 58(1)：1. ［10］ MENG Fan-xin, QIN Chen, DAI Kang, et al(孟繁新,秦 晨，戴 康，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2007，27(12)：2393. ［11］ Mitchell A C G, Zemansky M W. Resonance Radiation and Excited Atoms. New York： Combridge University Press, 1971. 116. ［12］ Davies J T, Vaughan J M. Astrophysics J., 1963, 137：1302. ［13］ Theodosiou C E. Phys. Rev., 1984, A30(6), 2881. ［14］ Smith D A, Hughes I!G. Am. J. Phys., 2004, 72(5)：631. ［15］ Horvatic V, Correll T L, Omenetto N, et al. Spectrochim Acta, 2006, B61： 1260. ［16］ Czajkowsisi M, McGillis D A, Krause L. Can. J. Phys., 1966, 44：91. ［17］ Gallagher A. Phys. Rev., 1968, 172：88.
