The fluorescence spectrum of cesium vapor was studied in a cell irradiated with the light of 852.3 nm resonance line from a single mode laser diode. From the intensities and spectra of the Cs and Cs2 fluorescence we identified several collisional and radiative processes in the excited cesium atom-dimer system. The atomic lines of the highly excited states were the result of collisional energy transfer from Cs(6P 3/2) + Cs(6P 3/2) to Cs(6D, 8S) atoms. The Cs2 (B 1 IIu) band formed in Cs (6P) + Cs2 (X1sigmag+) collisions. The fine-structure mixing in 6 2P atoms was studied through excitation transfer, energy-pooling collision, and collisional excitation transfer between Cs2 and Cs. The authors estimated the value of rate coefficient for the collisional energy transfer from 6P3/2 to 6P1/2 to be (5.2+/-2.1) x 10(-11) cm3 x s(-1). For the excitation transfer process Cs2 (B 1 IIu)+ Cs(6S)--> Cs2 (X 1sigmag+) + Cs(6P1/2 ), a rate coefficient of (1.0+/-0.4) x 10(-9) cm3 x s(-1) was yielded.
The fluorescence spectrum of cesium vapor was studied in a cell irradiated with the light of 852.3 nm resonance line from a single mode laser diode. From the intensities and spectra of the Cs and Cs2 fluorescence we identified several collisional and radiative processes in the excited cesium atom-dimer system. The atomic lines of the highly excited states were the result of collisional energy transfer from Cs(6P 3/2) + Cs(6P 3/2) to Cs(6D, 8S) atoms. The Cs2 (B 1 IIu) band formed in Cs (6P) + Cs2 (X1sigmag+) collisions. The fine-structure mixing in 6 2P atoms was studied through excitation transfer, energy-pooling collision, and collisional excitation transfer between Cs2 and Cs. The authors estimated the value of rate coefficient for the collisional energy transfer from 6P3/2 to 6P1/2 to be (5.2+/-2.1) x 10(-11) cm3 x s(-1). For the excitation transfer process Cs2 (B 1 IIu)+ Cs(6S)--> Cs2 (X 1sigmag+) + Cs(6P1/2 ), a rate coefficient of (1.0+/-0.4) x 10(-9) cm3 x s(-1) was yielded.
Using stepwise excitation of the cesium 8S atoms level in Cs vapor,several collisional and radiative processes have been identified from the intensities and spectra of the Cs fluorescence.The 5D state was populated by 8S→7P→5D transitions.In cesium densities 1016-1017?cm-3,the energy pooling collisions 5D+5D→nL+6S(nL=9D,11S,7F are studied.Since the 5D→6P(3.0-3.6 μm) fluorescence could not be detected with this experiment,the EP rate coefficients have been measured relative to the known rate coefficient of the collision,i.e.,6P+5D→6S+7D.The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode laser beam,tuned to 6P3/2→8S1/2 transition,which could be translated parallel to the pump beam.The excited atom densities are combined with measured fluorescene ratios to determine cross sections for the cesium energy pooling process.The average values(in units of 10-10?cm3s-1) for nL=9D,11S and 7F are 8.4±4.2,7.3±3.6,and 9.7±4.8,respectively.Influence on k11S and k7F of the energy transfer process 11S+6S7F+6S is also dicussed.
Populations of the n 2L(nL=7p,6D)states of Cs atoms by photodissociation of Cs_2 molecules through the use of the fixed frequence line 441.6nm of a He-Cd laser radiation are produced.Combining ratios of atomic to molecular fluorescence at the Cs density range between 1 and 9×10 15 cm -3 ,the ratios of collisional excitation transfer rate coefficients and the predissociation rates are obtained.The cross section for the fine-structure-changing collision [i.e,Cs(7P_ 1/2 )+Cs(6S)Cs(7P_ 3/2 )+Cs(6S)]is 3.5×10 -14 cm 2.
Using selective stepwise excitation of the cesium 8S atomic level in Cs vapor, the collisional transfer and the population of the high-lying atomic states were studied in detail. At cesium densities of 10(16)-10(17) cm(-3), the rate coefficient of excitation collision [i. e., 8S+6S --> 6D+6S] was measured. Measurement of fluorescence intensities as a function of Cs density yields k6D = (2.4 +/- 0.5) x 10(-10) cm3 x s(-1). The 5D state was populated by the 8S --> 7P --> 5D transitions. The energy pooling collisions 5D+5D --> nL+6S (nL = 9D, 11S, 7F) were also studied. The rate coefficients were measured relative to the known rate coefficient of the collision [i. e. 6P+5D --> 6S+7D]. The densities of 6P state were combined with measured fluorescence ratios to determine rate coefficients for EP process. The average values (in unites of 10(-10) cm3 x s(-1)) for nL = 9D, 11S and 7F are 6.4 +/- 3.2, 1.0 +/- 0.5 and 8.4 +/- 4.2, respectively.
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 6P1 --> 8S(1/2) 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 6P --> 6S(1/2) transitions. The N2 caused line broadening and therefore increased the effective pumping rate and radiative rates. The effective radiative rates were calculated for the 6P(J) --> 6S transitions. The fluorescence intensity I895 of the sensitized 6P(1/2) --> 6S(1/2) emission was measured as a function of N2 density in the range 2 x 10(16) < N < 1.4 x 10(17) cm(-3) at a constant temperature T = 337 K, which produced cesium density N0 = 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 N2 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 6P(J) 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 sigma3/2 --> 1/2 = (0.42 +/- 0.17) x 10(-16) cm2 and sigmaD = (1.31 +/- 0.52) x 10(-16) cm2 for the 6P(J) 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 we have recently obtained under different experimental conditions.
By applying the laser absorption and fluorescence method,the cross sections for the fine structure mixing and quenching of the Cs(6P) state,induced by collision with He atoms,have been 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,which was tuned to the 6PJ→8S1/2 transitions.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 He density in the range 0.5×1018～4×1018cm-3 at constant temperature T=337 K.It was found that the quantity N/I895 exhibited a parabolic dependence on N,confirming that the quenching of the 6PJ states was due to collision with He atoms,not ground state Cs atoms.The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ3/2→1/2=(1.46±0.51)×10-19 cm2 and σD=(2.28±0.80)×10-18 cm2 for the 6PJ fine structure mixing and quenching,respectively,due to collision with He atoms.
Fine-structure mixing in 62P Cs atoms is studie d throu gh excitation transfer and energy-pooling collision. Cs atoms were excited to t he 6P__ 3/2 level using a single-mode laser diode. The resulting fluo r escence included a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state and the energy-pooling collisions. Measurement of relative intensities of the two components yielded the following cross section: σ(6P__ 3/2 →6P__ 1/2 )=(1.5±0.5)×10 -15 *cm2. Comparisons of our res ult with other experiments have been made.