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Journal of Atomic and Molecular Physics

Radiative transport and collisional transfer of excitation energy in Rb(5P)atoms mixed with N_2

Shen Yi

Published Jan 1, 2008• 0 citations
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Abstract

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.

Related papers

Mixture and Quenching of the Rb (5P_J) States Induced by Collisions with Helium Atoms

Yifan Shen

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.

Shinjang dashösi ilmiy jurnili•Jan 1, 2007•0 citations

[Radiative transport and collisional transfer of excitation energy in Cs(6P) atoms mixed with N2].

Fanxin Meng, Qin Chen, Kang Dai +1 more

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.

•May 1, 2008•0 citations

Radiation and Collision Energy Transfer of Excitated Cs(6P) Atoms Mixed with He

Yifan Shen

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.

Chinese Journal of Lasers•Jan 1, 2007•0 citations

Mixing and quenching of the Cs 5DJstates induced by collisions with caesium ground-state atoms

Mladen Movre, Cedomil Vadla, Vlasta Horvatić

Applying the cw laser absorption and fluorescence method the cross sections for the fine-structure mixing and quenching of the caesium 5D J states have been measured in pure caesium vapour. Caesium atoms were optically excited to the 5D 5/2 state via the quadrupole-allowed 6S 1/2 →5D 5/2 transition. The ground-state caesium density N 0 , obtained from the absorption at the pumped quadrupole transition, and the fluorescence intensity I 689 of the sensitized 5D 3/2 →6S 1/2 emission were measured simultaneously in the range 3×10 14 cm -3 ⩽ N 0 ⩽1×10 16 cm -3 at constant temperature T = 585 K. It was found that the quantity N 0 2 / I 689 exhibited a parabolic dependence on N 0 , confirming that the quenching of the Cs 5D J states is due to collisions with Cs ground-state atoms, not molecules. The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ 5/2→3/2 = (57±19)×10 -16 cm 2 and σ D = (35±10)×10 -16 cm 2 for the Cs 5D J fine-structure mixing and quenching, respectively, due to collisions with caesium ground-state atoms. Using recently calculated Cs*+Cs potentials we performed an analysis which shows good agreement between the measured values and the theoretical predictions.

Journal of Physics B Atomic Molecular and Optical Physics•Jul 27, 2000•3 citations

[Mixing and quenching of Rb 5PJ states induced by collisions with He atoms and N2 molecules].

Fanxin Meng, Qin Chen, Kang Dai +1 more

The collisional energy transfer process Rb(5PJ)+M, where M= He, N2, under gas cell conditions has been investigated. The Rb(5P3/2) state was excited by a diode laser. The direct 5P3/2-->5S1/2 fluorescence and the sensitized 5P1/2-->5S1/2 fluorescence as a function of quenching gas pressure were measured. The 5P3/2 and 5P1/2 states are separated by 238 cm(-1). The closest other states are >6500 cm(-1) or >28 KT. Neglect of these other states should be an excellent approximation. In the experiment the Rb density was 4.5 x 10(11) cm(-3). Using radiation trapping theory the effective radiative rate=Gammae5P3/2-->5S1/2 2.47 x 10(7) s(-1) was obtained. For quenching by He only electronic to translational energy transfer is possible. However, in the N2 case, electronic to vibrational or rotational transfer is important. The Rb(5P3/2) state is 13 cm(-1) lower than the N2[X'Sigmag+ (V= 5, J= 11)]state; this energy gap is near resonant. The authors have not attempted to directly observe this possible E-R quenching channel Using a two-state rate equation model the transfer rate coefficients from Rb(5PJ) were obtained. The rate coefficient (k21He) for 5P3/2-->5P1/2 transfer in collision with He is 2.61 x 10(-12) cm3 x s(-1). By comparing the direct and sensitized fluorescence intensities for He and N2 case, and fitting the experimental results to the rate equation analysis, the authors estimate that the rate coefficient (k21N2) for 5P3/2-5P1/2 transfer in collision with N2 is 2.36 x 10(-11) cm3 x s(-1). The E-V quenching rate coefficient (kN2) of the 5PJ state is 1.44 x 10(-10) cm3 x s(-1). The authors found find that the rate coefficient kN2 is about 6 times larger than the k21N2. The assumption that the Cs-N2 energy transfer occurs primarily in collinear collision geometry is supported. The results are discussed in relation to those of other experiments.

•Dec 1, 2007•0 citations

Fine-structure mixing in 5~2P Rb atoms studied through excitation transfer and energy-pooling collisions

Yifan Shen

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.

Chinese Journal of Quantum Electronics•Jan 1, 2005•1 citation
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.
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.
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.
Applying the cw laser absorption and fluorescence method the cross sections for the fine-structure mixing and quenching of the caesium 5D J states have been measured in pure caesium vapour. Caesium atoms were optically excited to the 5D 5/2 state via the quadrupole-allowed 6S 1/2 →5D 5/2 transition. The ground-state caesium density N 0 , obtained from the absorption at the pumped quadrupole transition, and the fluorescence intensity I 689 of the sensitized 5D 3/2 →6S 1/2 emission were measured simultaneously in the range 3×10 14 cm -3 ⩽ N 0 ⩽1×10 16 cm -3 at constant temperature T = 585 K. It was found that the quantity N 0 2 / I 689 exhibited a parabolic dependence on N 0 , confirming that the quenching of the Cs 5D J states is due to collisions with Cs ground-state atoms, not molecules. The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ 5/2→3/2 = (57±19)×10 -16 cm 2 and σ D = (35±10)×10 -16 cm 2 for the Cs 5D J fine-structure mixing and quenching, respectively, due to collisions with caesium ground-state atoms. Using recently calculated Cs*+Cs potentials we performed an analysis which shows good agreement between the measured values and the theoretical predictions.
The collisional energy transfer process Rb(5PJ)+M, where M= He, N2, under gas cell conditions has been investigated. The Rb(5P3/2) state was excited by a diode laser. The direct 5P3/2-->5S1/2 fluorescence and the sensitized 5P1/2-->5S1/2 fluorescence as a function of quenching gas pressure were measured. The 5P3/2 and 5P1/2 states are separated by 238 cm(-1). The closest other states are >6500 cm(-1) or >28 KT. Neglect of these other states should be an excellent approximation. In the experiment the Rb density was 4.5 x 10(11) cm(-3). Using radiation trapping theory the effective radiative rate=Gammae5P3/2-->5S1/2 2.47 x 10(7) s(-1) was obtained. For quenching by He only electronic to translational energy transfer is possible. However, in the N2 case, electronic to vibrational or rotational transfer is important. The Rb(5P3/2) state is 13 cm(-1) lower than the N2[X'Sigmag+ (V= 5, J= 11)]state; this energy gap is near resonant. The authors have not attempted to directly observe this possible E-R quenching channel Using a two-state rate equation model the transfer rate coefficients from Rb(5PJ) were obtained. The rate coefficient (k21He) for 5P3/2-->5P1/2 transfer in collision with He is 2.61 x 10(-12) cm3 x s(-1). By comparing the direct and sensitized fluorescence intensities for He and N2 case, and fitting the experimental results to the rate equation analysis, the authors estimate that the rate coefficient (k21N2) for 5P3/2-5P1/2 transfer in collision with N2 is 2.36 x 10(-11) cm3 x s(-1). The E-V quenching rate coefficient (kN2) of the 5PJ state is 1.44 x 10(-10) cm3 x s(-1). The authors found find that the rate coefficient kN2 is about 6 times larger than the k21N2. The assumption that the Cs-N2 energy transfer occurs primarily in collinear collision geometry is supported. The results are discussed in relation to those of other experiments.
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.