Rb atoms were excited to the 5P3/2 level using a single-mode laser diode. The 5P3/2 state atom density was measured by the absorption of line from a Rb hollow-cathode lamp. The excited atom density is combined with measured fluorescence ratio to determine collisional cross section for the energy pooling process [i.e. Rb(5P3/2)+Rb(5P3/2)→Rb(5D)+Rb(5S)]. The cross section is (5.0±1.9)(?)10-14cm2. Cross section for 5P3/2 →5P1/2 transfer in Rb, induced in collision with ground-state Rb atoms, has been determined using methods of atomic fluorescence. The resulting fluorescence 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(5P3/2→5P1/2)=(3.0±0.9)×10-15cm2. It is found that the rate for the energy pooling is an order of magnitude more efficient than 5P3/2→5P1/2 mixture. Comparisons of our result with other experiments have been made.
Rb atoms were excited to the 5P3/2 level using a single-mode laser diode. The 5P3/2 state atom density was measured by the absorption of line from a Rb hollow-cathode lamp. The excited atom density is combined with measured fluorescence ratio to determine collisional cross section for the energy pooling process [i.e. Rb(5P3/2)+Rb(5P3/2)→Rb(5D)+Rb(5S)]. The cross section is (5.0±1.9)(?)10-14cm2. Cross section for 5P3/2 →5P1/2 transfer in Rb, induced in collision with ground-state Rb atoms, has been determined using methods of atomic fluorescence. The resulting fluorescence 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(5P3/2→5P1/2)=(3.0±0.9)×10-15cm2. It is found that the rate for the energy pooling is an order of magnitude more efficient than 5P3/2→5P1/2 mixture. Comparisons of our result with other experiments have been made.
Energy pooling (EP) was observed in Rb vapor following pulsed optical excitation to the 5P1/2 state. The 5P3/2 state was populated by the energy transfer process: Rb(5P1/2)+Rb(5S1/2) --> Rb(5P3/2)+Rb(5Sl/2). The resulting densities of Rb atoms at the 5P1/2 level were obtained from the absorption of narrow spectral line from a Rb hollow cathode lamp, connecting the 5P1/2 state to 7S state. Since the effective lifetimes of the 5P1/2 and 5P3/2 states are approximately equal, the densities of the 5P3/2 level were obtained from the D2 to D1 fluorescence ratios where D1 and D2 are lines of the 5P1/2 --> 5S1/2 and 5P3/2 --> 5S1/2 transition. Because the time of the fine structure exchanging is much shorter than the lifetime of the 5D state, the fluorescence originating from the 5D state produced by the 5P1/2 + 5P3/2 and 5P3/2 + 5P3/2 processes follows the instantaneous production rate of the 5P1/2 + 5P1/2 process. It is clear that 5P/2 + 5P3/2 and 5P3/2 + 5P3/2 collisions can significantly influence the results obtained for the 5P1/2 + 5P1/2 rate since the energy defect for 5D state is much smaller for 5P1/2 + 5P3/2 and 5P3/2 + 5P3/2 collisions than for 5P1/2 + 5P1/2 collisions. Effective lifetimes of the 5P levels were calculated using radiation trapping theory. The time-integrated populations and signals were studied and analyzed. The resulting fluorescence included the direct component emitted in the decay of the optically excited 5P1/2 state and the sensitized component arising from the collisions for populating 5D state at different cell temperature. These relative intensities were combined with the measured excited atom densities to yield absolute energy-pooling rate coefficients. The cross sections (in units of 10(-14) cm2) for the energy-pooling collisions [i. e. , 5P1/2 + 5P1/2, 5P1/2 + 5P3/2, 5P3/2 + 5P3/2] are 0.78, 2.9 and 3.1, respectively. The dependence of the rates upon energy defect deltaE was examined, but the 5D3/2 level was approximately equally populated in 5P3/2 + 5P3/2 (deltaE = 68 cm(-1)) and 5P3/2 + 5P1/2 (deltaE = 306 cm(-1)) collisions. The 5P1/2 + 5P3/2 collisions are as efficient as 5P3/2 + 5P3/2 for populating 5D3/2 state.
Applying the CW laser absorption and fluorescence method,the cross sections for the fine structure mixing and quenching of the Rb(5P)state,induced by collision with N2 molecules,have been measured.Cesium atoms were optically excited to the 5P3/2 state.The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam,turned to the 5PJ→7S1/2 transitions.The effective radiative rates were calculated for the 5PJ→5S transitions.The fluorescence intensity I794 of the sensitized 5P1/2→5S1/2 emission was measured as a function of N2 density in the range 0.5×1016N4×1016cm-3 at constant temperature T=340 K.It was found that the quantity N/I794 exhibited a parabolic dependence on N,confirming that the quenching of the 5PJ states is due to collision with N2 molecules,not Rb ground state atoms.The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ3/2→1/2=(10.43±3.54)×10-16cm2 and σD=(9.8±3.4)×10-16cm2 for the 5PJ fine-structure mixing and quenching,respectively,due to collision with N2 atoms.Our values for these cross sections are in agreement,within combined error bars,with values we have recently obtained under different experimental conditions.
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.
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.
Rb vapor was irradiated in a glass fluorescence cell with pulses of radiation from a YAG laserpumped OPO laser,populating 5D_j(or 7S) state by two-photon absorption.Energy transfer in Rb (5D_J,7S)+Rb(5S) collision is studied using methods of atomic fluorescence.The resulting fluorescence includes a direct component emitted in the optically excited state decay and a sensitized component arsing. from the collisional populated state.At the different densities of the components,fitting a three-state rate equation model,the cross sectionσ=(3.7±0.9)×10~(-14) cm~2 was obtained for Rb(5D_(5/2))→Rb(5D_(3/2)) transfer.The cross section for excitation transfer out of the 5D_J doublet are(3.1±1.2)×10~(-14) cm~2(for J = 5/2) and(2.0±0.6)×10~(-14) cm~2(for J = 3/2),respectively.The energy transfer cross section for the Rb(5D)→Rb(7S) is small,(1.6±0.4)×10~(-16) cm~2.The 5D_J state is quenched mainly in the reverse energy pooling processes,i.e.Rb(5D_J)+Rb(5S)→Rb(5P)+ Rb(5P).
Applying the cw laser absorption and fluorescence method,the cross sections for the fine structure mixing and quenching of the Rb(5PJ) state,induced by collisions with He atoms have been measured,Rubidium atoms were optically excited to 5 P3/2states.The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam,tuned to the 5PJ→ 7S1/2 transitions.Transmission factors were calculated for the 5PJ→ 5S transitions.The fluorescence intensity I795 of the sensitized 5P1/2→ 5S1/2emission was measured as a function of He density in the range 0.5×1017 N 4× 1017cm-3at constant temperature T = 340 K.It was found that the quantity N/ I795 exhibited a parabolic dependence on N,confirming that the quenching of the 5PJ states is due to collision with He atoms,not due to Rb ground state atoms.The coefficients of the second-order polynomial fitted through the measured date yielded the cross sectionsσ3/2→1/2=(1.84± 0.61)× 10-17cm2 andσD=(1.07± 0.30)× 10-17cm2 for the 5PJfine-structure mixing and quenching,respectively,due to collision with He atoms.