Cesium molecules are pumped by a CW dye laser. Some of the excited molecules then pre-dissociate or collisionally transfer excitation to produce excited atoms at the 5D and 6P levels. The cross sections (in units of 10-14cm2) for the excitation transfer process Cs(6P)+Cs(5D) →Cs(7DJ)+Cs(6S)for J being 5/2 and 3/2 are 5. 4 ± 50% and 4. 9 ± 50%, respectively. The cross sections (in units of 10-14cm2) for the excitation transfer out of the 7D doublet [i. e. , Cs(7DJ)+Cs(6S) →states other than Cs(7D)] for J being 5/2 and 3/2 are 1. 6 ±50% and 0. 34±50%, respectively. To obtain these cross sections, the intensities of 7D and 5D fluorescence emissions and the 6P atom density are measured by using the absorption equivalent width technique. The results are discussed in eomparison with those of other experiments.
Cesium molecules are pumped by a CW dye laser. Some of the excited molecules then pre-dissociate or collisionally transfer excitation to produce excited atoms at the 5D and 6P levels. The cross sections (in units of 10-14cm2) for the excitation transfer process Cs(6P)+Cs(5D) →Cs(7DJ)+Cs(6S)for J being 5/2 and 3/2 are 5. 4 ± 50% and 4. 9 ± 50%, respectively. The cross sections (in units of 10-14cm2) for the excitation transfer out of the 7D doublet [i. e. , Cs(7DJ)+Cs(6S) →states other than Cs(7D)] for J being 5/2 and 3/2 are 1. 6 ±50% and 0. 34±50%, respectively. To obtain these cross sections, the intensities of 7D and 5D fluorescence emissions and the 6P atom density are measured by using the absorption equivalent width technique. The results are discussed in eomparison with those of other experiments.
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.
At a Cs density higher than 9 x 10(14) cm(-3), cesium vapor was irradiated in a glass fluorescence cell with pulses of radiation from an YAG-laser-pumped OPO laser, populating 6D(5/2) state by two-photon absorption. Energy transfer in Cs6(D(5/2)) + Cs (6S) collisions was studied using methods of atomic fluorescence. At the different Cs densities, we have measured the time-integrated intensities of the components and fitted a three-state rate equation model to obtain the cross sections. The experimental points were fitted to a straight line very well. The authors converted the gradient and intercept into cross sections. The cross section for 6D(5/2)-->6D(3/2) transfer is (2.1 +/- 0.4) x 10(14) cm2. The cross section for excitation transfer out of the 6D doublet is sigmaQ = (1.6 +/- 0.4) x 10(-14) cm2. The cross section on contains information on reverse energy pooling collisions [i.e., Cs(6D(3/2)) + Cs (6S(1/2))-->Cs(6P) + 6Cs(P)] and contribution from mining in 6Dj-->7P(J'), This latter contribution could be subtracted out using the results of a second experiment. At a Cs density lower than 6.0 x 10(12) cm3, the laser was used to pump the 6D(3/2) and 6D(5/2) states, respectively. The resulting fluorescence included the direct component emitted in the decay of the 6D(J) state and the sensitized component arising from the collisionally populated 7P(J') state. Relative intensities of the components yielded the cross sections. The cross-sections for the processes Cs(6D(5/2)) + Cs(6S(1/2))-->Cs(7P(J')) + Cs(6S(1/2)) are (1.6 +/- 0.5) x 10(-15) cm2. for J'= 3/2 and (6.5 +/- 2.1) x 10(-16) cm2, for J' = 1/2, respectively. The cross-sections for the processes Cs(6D(3/2) + Cs(6S(1/2))-->Cs (7P(J')) + Cs(6S(1/2)) are (1.9 +/- 0.6) x 10(-15) cm2. for J' = 3/2 and (7.6 + 2.4) x 10(-16) cm2, for J' = 1/2, respectively. The 6D(J) -->7P(J'), energy transfer rate coefficient is small. The total quenching rate coefficient out of the 6D(J) state is much larger. Evidence suggests that the quenching of the 6D(J) state is caused predominantly by reverse energy-pooling process. The cross section for this process, i.e., Cs(6D(3/2))+Cs(6S(1/2))-->Cs(6P) + Cs(6P) is (1.3 +/- 0.4) x 10(-14) cm2.
We report experimentally the measured rate coefficients for the energy pooling (EP) collisions process Cs(5D)+Cs(5D)-gCs(6S)+Cs(nL=9D,11S,7F) in cesium densities of 10^(16)-10^(17) cm^(-3). The 5D state was populated via 8S-g7P-g5D spontaneous emission following two-step pumping 6S-g6P_(3/2)-g8S. Since the 5D-g6P (3.0-3.6 microns) fluorescence could not be detected in this experiment, we carried out a relative measurement for the process 6P+5D-g6S+7D. The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode laser beam, tuned to 6P_(3/2)-g9S_(1/2) transition, which could be translated parallelly to the pump beam. The excited atom densities have been combined with the measured fluorescence ratios to yield EP rate coefficients. The average values for nL=9D,11S and 7F are 8.0+-4.0, 7.0+-3.5, and 9.3+-4.6 (in units of 10^(-10) cm3/s), respectively. Influence of the energy transfer process 11S+6S-g7F+6S on the rate coefficients k_(11S) and k_(7F) is also discussed.
Aim An experimental study into cesium energy pooling collision,Cs(6P3/2)+Cs(6P3/2)→Cs(nLJ=8S1/2,4F5/2,4F7/2)+Cs(6S1/2),has been carried out in a cell.Methods A single mode semiconductor laser is used to excite the 6P3/2 state,the other single mode laser antiparallel to pumping laser is used as absorption line to detect excited atomic intensity and its spatial distribution,with absorption line transiting from 6P3/2 to 8S1/2 and parallel to the movement of pumping laser.The cross section of energy pooling collisions is obtained by the ratio of the excited atomic density to fluorescence intensity of the spectral line.Results The cross sections of 8S1/2,4F5/2 and 4F7/2 are(5.43±1.56)×10-16 cm2,(4.89±1.16)×10-16 cm2 and(6.17±1.60)×10-16 cm2,respectively.Conclusion Compared with other test results,the calculation results are exact.
We report an experimental investigation of the excitation-transfer collision Cs(5D5/2)+Cs(6S)\ensuremath{\rightarrow}CS ((5D3/2)+Cs(6S). The upper 5D5/2 state was excited by a cw dye laser tuned to the one-photon, quadrupole-allowed 6S\ensuremath{\rightarrow}5D5/2 transition. Since the direct 5D\ensuremath{\rightarrow}6P fluorescence could not be detected with our apparatus, we monitored instead the cascade 6P\ensuremath{\rightarrow}6S fluorescence. The ratio of 6P1/2 to 6P3/2 fluorescence contains information on the collisional mixing that takes place in the 5D levels but also includes a significant contribution from mixing in the 6P levels. This latter contribution could effectively be subtracted out using the results of a second experiment in which a tunable cw diode laser was used to pump the 6P3/2 state, and the same fluorescence ratio monitored. The 5D mixing cross section we obtain, 70 A˚2, is significantly larger than previous indirect determinations.
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.