Journal of Physics B Atomic Molecular and Optical Physics
Experimental study of caesium energy pooling collisions and modelling of the excited atom density in the presence of optical pumping and radiation trapping
F. De Tomasi, Slobodan Milošević, Philippe Verkerk, A. Fioretti, M. Allegrini, Z. J. Jabbour, John Huennekens
An experimental study of caesium energy pooling collisions, , at thermal energies, has been carried out in a capillary cell using diode laser excitation. Use of the capillary cell minimizes the effects of radiation trapping, but nonetheless, such effects still play a significant role in the analysis. Consequently, a rate equation model, which treats simultaneous effects of saturation, optical pumping, and radiation trapping, has been developed and is used to determine the atom density under these experimental conditions. The excited atom densities are combined with measured fluorescence ratios to determine rate coefficients for the caesium energy pooling process. Our values for these rate coefficients are in agreement, within combined error bars, with values we have recently obtained under very different experimental conditions.
An experimental study of caesium energy pooling collisions, , at thermal energies, has been carried out in a capillary cell using diode laser excitation. Use of the capillary cell minimizes the effects of radiation trapping, but nonetheless, such effects still play a significant role in the analysis. Consequently, a rate equation model, which treats simultaneous effects of saturation, optical pumping, and radiation trapping, has been developed and is used to determine the atom density under these experimental conditions. The excited atom densities are combined with measured fluorescence ratios to determine rate coefficients for the caesium energy pooling process. Our values for these rate coefficients are in agreement, within combined error bars, with values we have recently obtained under very different experimental conditions.
An experimental study of caesium energy pooling collisions, Cs(6PJ ) + Cs(6PJ ) ! Cs(7PJ0 ) + Cs(6S1=2), at thermal energies, has been carried out in a capillary cell using diode laser excitation. Use of the capillary cell minimizes the effects of radiation trapping, but nonetheless, such effects still play a significant role in the analysis. Consequently, a rate equation model, which treats simultaneous effects of saturation, optical pumping, and radiation trapping, has been developed and is used to determine the Cs(6PJ ) atom density under these experimental conditions. The excited atom densities are combined with measured fluorescence ratios to determine rate coefficients for the caesium energy pooling process. Our values for these rate coefficients are in agreement, within combined error bars, with values we have recently obtained under very different experimental conditions.
An experimental study of rubidium energy pooling collisions,5P_J+5P_J′→5S+5D_J″,at thermal energies,has been carried out in a cell.Atoms were excited to either the 5P_1/2 or 5P_3/2 state using a single-mode diode laser.The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam,tuned to either 5P_1/2→5D_3/2,5P_3/2→7S_1/2 transition,which could be translated parallel to the pump beam.The excited atom densities are combined with measured fluorescence ratios to determine cross sections for the rubidium energy pooling process 5P_J+5P_J′→5S+5D_J″.Two tunable cw diode lasers were used to excite 5P_1/2 and 5P_3/2 respectively and the 5D_J″→5P_J fluorescence intensities were measured.For 5P_3/2+5P_1/2 collisions the cross sections for 5D_5/2,5D_3/2 are(1.12±0.50)×10~-14 and(1.01±0.45)×10~-14 cm~2,respectively.
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.
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.
We report experimental rate coefficients for the energy-pooling collisions Cs(6P1/2)+Cs(6P1/2)\ensuremath{\rightarrow}Cs(6S1/2)+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) and Cs(6P3/2)+Cs(6P3/2)\ensuremath{\rightarrow}Cs(6S1/2)+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) where ${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$=7P1/2, 7P3/2, 6D3/2, 6D5/2, 8S1/2, 4F5/2, or 4F7/2. Atoms were excited to either the 6P1/2 or 6P3/2 state using a single-mode Ti:sapphire laser. The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode ring dye laser beam, tuned to either the 6P1/2\ensuremath{\rightarrow}8S1/2 or 6P3/2\ensuremath{\rightarrow}7D3/2,5/2 transitions, which could be translated parallel to the pump beam. 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 all relevant transitions. Effective lifetimes of levels populated by energy-pooling collisions are modified by radiation trapping, and these factors were calculated using the Molisch theory. These calculated quantities have been combined with the measured excited-atom densities and fluorescence ratios to yield absolute energy-pooling rate coefficients. It was found that the rate for production, in all cases, is greatest for 6D, but that 1/2-1/2 collisions are significantly more efficient than 3/2-3/2 collisions for populating 7P. It was also found that 7P1/2 is populated two to three times more efficiently than 7P3/2 in 1/2-1/2 collisions, but that the 7P fine-structure levels are approximately equally populated in 3/2-3/2 collisions. \textcopyright{} 1996 The American Physical Society.
We experimentally study rubidium energy pooling collisions of Rb(5 P 3/2 )+Rb(5 P 3/2 )→Rb(5 S 1/2 )+Rb ( nl J = 5 D J ,7 S 1/2 ) at low densities in a cell using diode laser excitation. The excited-atom density and spatial distribution are mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam, tuned to the 5 P 3/2 →7 S 1/2 transition, which could be translated parallel to the pump beam. The excited atom densities are combined with measured fluorescence ratios to determine cross sections for the rubidium energy pooling process. The cross sections for nl J being 5 D 5/2 , 5 D 3/2 , and 7 S 1/2 are (1.32±0.59) × 10 −14 , (1.18±0.53) × 10 −14 and (3.21±1.44) × 10 −15 cm 2 , respectively.