Cs(6P)激发态的辐射及与N2碰撞的能量转移  

Radiative Transport and Collisional Transfer of Excitation Energy in Cs(6P) Atoms Mixed with N_2

作　　者：孟繁新[1] 秦晨[1] 戴康[1] 沈异凡[1] 

机构地区：[1]新疆大学物理科学与技术学院

出　　处：《光谱学与光谱分析》2008年第5期974-977,共4页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金资助(10264004)项目

摘　　要：应用激光吸收和荧光方法,测量了Cs(6P)态与N2碰撞的精细结构转移和碰撞猝灭截面。Cs原子被激光激发到6P3/2态,将与泵浦激光束反向平行的检测激光束调到6PJ→8S1/2的跃迁,测量了6PJ激发态的密度及空间分布,由此计算了6PJ→6S的有效辐射率。在T=337 K(蒸气压公式给出Cs密度N0=1.25×1012cm-3)和N2密度2×1016<N<1.4×1017cm-3范围内测量了6P1/2→6S1/2(895 nm)发射的敏化荧光强度I895。量N/I895(I895经过样品池透明度修正)与N有抛物线型的关系,表明了6PJ的猝灭是由于与N2分子的碰撞产生的,而不是由与Cs基态原子碰撞产生的。N2的引入,一方面产生原子激发态的碰撞转移;另一方面由于谱线的碰撞增宽,增大了有效泵浦率和有效辐射率。由最小二乘法确定的二次多项式的系数得到6P态与N2碰撞精细结构转移截面σ3/2→1/2=(0.42±0.17)×10-16cm2,猝灭截面σD=(1.31±0.52)×10-16cm2,与在不同的实验条件下得到的结果在误差范围内一致。Applying the CW laser absorption and fluorescence method, the cross sections for the fine structure mixing and quenching of the Cs（6P） state, induced by collision with N2 molecules, were measured. Cesium atoms were optically excited to the 6P3/2 state. The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam, tuned to the 6Pj→8S1/2 transitions, which could be translated parallel to the pump beam. The transmission factors, which describe the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed, were calculated for 6Pj→6S1/2 transitions. The N2 caused line broadening and therefore increased the effective pumping rate and radiative rates. The effective radiative rates were calculated for the 6Pj→6S transitions. The fluorescence intensity I895 of the sensitized 6P1/2→6S1/2 emission was measured as a function of N2 density in the range 2X10^16〈N〈1.4X 10^17cm^-3 at a constant temperature T=337 K, which produced cesium density No = 1.25 X 10^12 cm^-3. The transparency of the cell was obtained by the absorption of light beam passing the cell. The transparency is not a simple function of Nz density. It was found that the quantity N/I895 （I895 being corrected for the cell transparency） exhibited a parabolic dependence on N, confirming that the quenching of the 6Pj states is due to collision with N2 molecules instead of Cs ground state atoms. The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ3/2→（0.42士0.17）×10-10^16cm^2 and = σD=（1.31土0.52）×10^16cm^2 for the 6 Pj fine-structure mixing and quenching, respectively, due to collision with N2 molecules. The quenching rate coefficient is about 3 times larger than the rate coefficient for the fine-structure mixing. Our values for these cross sections are in agreement, within combined error bars, with the values w

关 键 词：碰撞能量转移 荧光 截面 铯 氮气 

分 类 号：O562.5[理学—原子与分子物理]