Physical Review A

Hyperfine state-changing collisions of Cs(6P1∕2) atoms with argon perturbers

L. Morgus, T. Morgus, Tyler Drake, John Huennekens

Published Mar 10, 2008• 3 citations

Abstract

A two-step excitation experiment has been employed to measure the collisional rate coefficients and to study the velocity distribution of $\mathrm{Cs}(6{P}_{1∕2})$ atoms that have undergone a single hyperfine state-changing collision with Ar. In addition, argon pressure broadening rates and shifts of the cesium $6{P}_{1∕2}({F}^{\ensuremath{'}})\ensuremath{\rightarrow}8{S}_{1∕2}({F}^{\ensuremath{''}})$ transitions have been determined. In the experiment, a single mode, cw Ti:sapphire laser is tuned to line center of the $6{S}_{1∕2}(F=4)\ensuremath{\rightarrow}6{P}_{1∕2}$(${F}^{\ensuremath{'}}=3$ or 4) transition. Then, the frequency of a single mode cw dye laser is scanned over the $6{P}_{1∕2}\ensuremath{\rightarrow}8{S}_{1∕2}$ manifold to probe the populations of the $6{P}_{1∕2}$ hyperfine levels. Absorption of probe laser photons is monitored by detecting $8{S}_{1∕2}\ensuremath{\rightarrow}6{P}_{3∕2}$ fluorescence. The experiment is conducted at room temperature, where the Cs density is low $(n\ensuremath{\sim}3.4\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$, and thus the probability of a $\mathrm{Cs}\text{\ensuremath{-}}\mathrm{Cs}$ collision is negligible during the $\mathrm{Cs}(6{P}_{1∕2})$ radiative lifetime. The Ar pressure is varied from 0 to $1.52\phantom{\rule{0.3em}{0ex}}\mathrm{Torr}$, and $\mathrm{Cs}\text{\ensuremath{-}}\mathrm{Ar}$ collisions cause population to be transferred from the directly excited $6{P}_{1∕2}({F}^{\ensuremath{'}})$ level to the other $6{P}_{1∕2}$ hyperfine level. The data are analyzed using a density matrix formalism to yield the rate coefficients for $\mathrm{Cs}(6{P}_{1∕2})\text{\ensuremath{-}}\mathrm{Ar}$ hyperfine state-changing collisions. In addition, the one-dimensional velocity changing collision kernel for $\mathrm{Cs}(6{P}_{1∕2})$ atoms prepared with ${v}_{z}=0$ that undergo ${F}^{\ensuremath{'}}=3\ensuremath{\leftrightarrow}{F}^{\ensuremath{'}}=4$ hyperfine state-changing collisions with argon is reported.

DOI: 10.1103/physreva.77.032704

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Energy-pooling collisions in cesium: 6 PJ +6 PJ →6S+(nl=7P,6D,8S,4F)

Z. J. Jabbour, R. K. Namiotka, John Huennekens +3 more

Physical Review AAug 1, 199663 citations

Radiation trapping and spatial distribution of the Cs(6P_(3/2)) atoms in the vapor mixed with Ar

Yifan Shen

Jiguang zazhiJan 1, 20080 citations

[Effect of saturation and velocity selective population in 6S1/2 --> 6P3/2 laser excitation in Cs vapor mixed with Ar].

Jing Liu, Heng-wei Zhou, Guoliang Zhang +2 more

Sep 1, 20080 citations

Energy transfer in collisions between two Cs(5D) atoms

Yifan Shen

Journal of Atomic and Molecular PhysicsJan 1, 20070 citations

Excitation-transfer collisions in cesium vapor: Cs(5 D5/2 )+Cs(6 S1/2 )→Cs (5 D3/2 )+ Cs(6 S1/2 )

B. Keramati, Mark F. Masters, John Huennekens

Physical Review ANov 1, 198810 citations

Energy-pooling collisions in cesium: 6{ital P}{sub {ital J}}+6{ital P}{sub {ital J}}{r_arrow}6{ital S}+({ital nl}=7{ital P},6{ital D},8{ital S},4{ital F})

Z. J. Jabbour, R. K. Namiotka, John Huennekens +3 more

Physical Review AAug 1, 199641 citations

Physical Review A

Hyperfine state-changing collisions of Cs(6P1∕2) atoms with argon perturbers

L. Morgus, T. Morgus, Tyler Drake, John Huennekens

Published Mar 10, 2008• 3 citations

Publisher

Abstract

A two-step excitation experiment has been employed to measure the collisional rate coefficients and to study the velocity distribution of

\mathrm{Cs}(6{P}_{1∕2})

atoms that have undergone a single hyperfine state-changing collision with Ar. In addition, argon pressure broadening rates and shifts of the cesium

6{P}_{1∕2}({F}^{\ensuremath{'}})\ensuremath{\rightarrow}8{S}_{1∕2}({F}^{\ensuremath{''}})

transitions have been determined. In the experiment, a single mode, cw Ti:sapphire laser is tuned to line center of the

6{S}_{1∕2}(F=4)\ensuremath{\rightarrow}6{P}_{1∕2}

(

{F}^{\ensuremath{'}}=3

or 4) transition. Then, the frequency of a single mode cw dye laser is scanned over the

6{P}_{1∕2}\ensuremath{\rightarrow}8{S}_{1∕2}

manifold to probe the populations of the

6{P}_{1∕2}

hyperfine levels. Absorption of probe laser photons is monitored by detecting

8{S}_{1∕2}\ensuremath{\rightarrow}6{P}_{3∕2}

fluorescence. The experiment is conducted at room temperature, where the Cs density is low

(n\ensuremath{\sim}3.4\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})

, and thus the probability of a

\mathrm{Cs}\text{\ensuremath{-}}\mathrm{Cs}

collision is negligible during the

\mathrm{Cs}(6{P}_{1∕2})

radiative lifetime. The Ar pressure is varied from 0 to

1.52\phantom{\rule{0.3em}{0ex}}\mathrm{Torr}

, and

\mathrm{Cs}\text{\ensuremath{-}}\mathrm{Ar}

collisions cause population to be transferred from the directly excited

6{P}_{1∕2}({F}^{\ensuremath{'}})

level to the other

6{P}_{1∕2}

hyperfine level. The data are analyzed using a density matrix formalism to yield the rate coefficients for

\mathrm{Cs}(6{P}_{1∕2})\text{\ensuremath{-}}\mathrm{Ar}

hyperfine state-changing collisions. In addition, the one-dimensional velocity changing collision kernel for

\mathrm{Cs}(6{P}_{1∕2})

atoms prepared with

{v}_{z}=0

that undergo

{F}^{\ensuremath{'}}=3\ensuremath{\leftrightarrow}{F}^{\ensuremath{'}}=4

hyperfine state-changing collisions with argon is reported.

DOI: 10.1103/physreva.77.032704

Related papers

Energy-pooling collisions in cesium: 6 PJ +6 PJ →6S+(nl=7P,6D,8S,4F)

Z. J. Jabbour, R. K. Namiotka, John Huennekens +3 more

We report experimental rate coefficients for the energy-pooling collisions Cs(6 ${\mathit{P}}_{1/2}$ )+Cs(6 ${\mathit{P}}_{1/2}$ )\ensuremath{\rightarrow}Cs(6 ${\mathit{S}}_{1/2}$ )+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) and Cs(6 ${\mathit{P}}_{3/2}$ )+Cs(6 ${\mathit{P}}_{3/2}$ )\ensuremath{\rightarrow}Cs(6 ${\mathit{S}}_{1/2}$ )+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) where ${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$=7 ${\mathit{P}}_{1/2}$ , 7 ${\mathit{P}}_{3/2}$ , 6 ${\mathit{D}}_{3/2}$ , 6 ${\mathit{D}}_{5/2}$ , 8 ${\mathit{S}}_{1/2}$ , 4 ${\mathit{F}}_{5/2}$ , or 4 ${\mathit{F}}_{7/2}$ . Atoms were excited to either the 6 ${\mathit{P}}_{1/2}$ or 6 ${\mathit{P}}_{3/2}$ 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 6 ${\mathit{P}}_{1/2}$ \ensuremath{\rightarrow}8 ${\mathit{S}}_{1/2}$ or 6 ${\mathit{P}}_{3/2}$ \ensuremath{\rightarrow}7 ${\mathit{D}}_{3/2,5/2}$ 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 7 ${\mathit{P}}_{1/2}$ is populated two to three times more efficiently than 7 ${\mathit{P}}_{3/2}$ 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 report experimental rate coefficients for the energy-pooling collisions Cs(6${\mathit{P}}_{1/2}$)+Cs(6${\mathit{P}}_{1/2}$)\ensuremath{\rightarrow}Cs(6${\mathit{S}}_{1/2}$)+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) and Cs(6${\mathit{P}}_{3/2}$)+Cs(6${\mathit{P}}_{3/2}$)\ensuremath{\rightarrow}Cs(6${\mathit{S}}_{1/2}$)+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) where ${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$=7${\mathit{P}}_{1/2}$, 7${\mathit{P}}_{3/2}$, 6${\mathit{D}}_{3/2}$, 6${\mathit{D}}_{5/2}$, 8${\mathit{S}}_{1/2}$, 4${\mathit{F}}_{5/2}$, or 4${\mathit{F}}_{7/2}$. Atoms were excited to either the 6${\mathit{P}}_{1/2}$ or 6${\mathit{P}}_{3/2}$ 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 6${\mathit{P}}_{1/2}$\ensuremath{\rightarrow}8${\mathit{S}}_{1/2}$ or 6${\mathit{P}}_{3/2}$\ensuremath{\rightarrow}7${\mathit{D}}_{3/2,5/2}$ 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 7${\mathit{P}}_{1/2}$ is populated two to three times more efficiently than 7${\mathit{P}}_{3/2}$ 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.

Physical Review AAug 1, 199663 citations

Radiation trapping and spatial distribution of the Cs(6P_(3/2)) atoms in the vapor mixed with Ar

Yifan Shen

The effective radiative rate for Cs(6P3/2) resonance level in the presence of Ar is determined.Cs atoms were excited to the 6P3/2 state using a single-mode diode laser(pump laser).The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam(probe laser),tuned to the 6P3/28S1/2 transition which could be translated parallel to the pump beam.In the presence of radiation trapping,the spontaneous radiation rate is multiplied by the transmission factor T6p3/26S1/2,which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed.Position dependent 6P3/2 state densities had been combined with the collisional broadening rate 6P3/26S1/2 line due to both Ar and cesium perturbers to yield the T6p3/26S1/2.The effective radiative rates of the Cs D2 line as a function of the Ar pressure PAr were obtained.The fluorescence intensity I852 of the 6P3/26S1/2emission was measured simultaneously.The measured fluorescence ratios determined the ratios of the effective radiative rates at different Ar density.These ratios are in agreement with theoretical evaluation.The effective radiative rate for Cs(6P3/2) resonance level in the presence of Ar is determined.Cs atoms were excited to the 6P3/2 state using a single-mode diode laser(pump laser).The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam(probe laser),tuned to the 6P3/28S1/2 transition which could be translated parallel to the pump beam.In the presence of radiation trapping,the spontaneous radiation rate is multiplied by the transmission factor T6p3/26S1/2,which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed.Position dependent 6P3/2 state densities had been combined with the collisional broadening rate 6P3/26S1/2 line due to both Ar and cesium perturbers to yield the T6p3/26S1/2.The effective radiative rates of the Cs D2 line as a function of the Ar pressure PAr were obtained.The fluorescence intensity I852 of the 6P3/26S1/2emission was measured simultaneously.The measured fluorescence ratios determined the ratios of the effective radiative rates at different Ar density.These ratios are in agreement with theoretical evaluation.

Jiguang zazhiJan 1, 20080 citations

[Effect of saturation and velocity selective population in 6S1/2 --> 6P3/2 laser excitation in Cs vapor mixed with Ar].

Jing Liu, Heng-wei Zhou, Guoliang Zhang +2 more

The excited state population distribution created by 6S1/2 --> 6P3/2 laser excitation in room temperature cesium vapor mixed with Ar was quantitatively analyzed applying absorption and saturation spectroscopy. A simple method for the determination of the excited state population in a single excitation step based on the measurements of the saturated and unsaturated absorption coefficients was tested. When the line profile is nearly pure Doppler and the laser linewidth is much smaller than the inhomogeneous linewidth but comparable with homogeneous linewidth, the fraction N(v(z)) of the atoms in the ground state that are able to absorb under inhomogeneous broadening conditions can be determined. The transmission of the medium in the center of the Doppler envelope of the strong h. f. component of the CsD2 line due to hyperfine pumping alone amounts to approximately 5%. The assumption that has been made is that the lower-state hyperfine levels are populated in a statistical ratio. The absorption coefficients were measured for a series of P852 powers between 20 microW and 2. 5 mW. The velocity selective population density in the 6P3/2 state was obtained. The population in the 6P3/2 level obtained from the saturation measurements was also determined by the absorption measurement of narrow spectral line from a Cs hollow cathode lamp. The agreement between the results obtained in these two ways is very good. It was shown that 5% of the ground state population could be transferred to the first excited state by pumping the Doppler broadened line with a single-mode narrow-band laser. The argon caused line broadening and therefore increased the effective pumping rate in the first excitation step. The dependence of the 852 nm line fluorescence intensity was plotted against the population in the 6P3/2 level determined from the saturation absorption. This can serve as confirmation of the reliability of the method used for the determination of the excited state population.The excited state population distribution created by 6S1/2 --> 6P3/2 laser excitation in room temperature cesium vapor mixed with Ar was quantitatively analyzed applying absorption and saturation spectroscopy. A simple method for the determination of the excited state population in a single excitation step based on the measurements of the saturated and unsaturated absorption coefficients was tested. When the line profile is nearly pure Doppler and the laser linewidth is much smaller than the inhomogeneous linewidth but comparable with homogeneous linewidth, the fraction N(v(z)) of the atoms in the ground state that are able to absorb under inhomogeneous broadening conditions can be determined. The transmission of the medium in the center of the Doppler envelope of the strong h. f. component of the CsD2 line due to hyperfine pumping alone amounts to approximately 5%. The assumption that has been made is that the lower-state hyperfine levels are populated in a statistical ratio. The absorption coefficients were measured for a series of P852 powers between 20 microW and 2. 5 mW. The velocity selective population density in the 6P3/2 state was obtained. The population in the 6P3/2 level obtained from the saturation measurements was also determined by the absorption measurement of narrow spectral line from a Cs hollow cathode lamp. The agreement between the results obtained in these two ways is very good. It was shown that 5% of the ground state population could be transferred to the first excited state by pumping the Doppler broadened line with a single-mode narrow-band laser. The argon caused line broadening and therefore increased the effective pumping rate in the first excitation step. The dependence of the 852 nm line fluorescence intensity was plotted against the population in the 6P3/2 level determined from the saturation absorption. This can serve as confirmation of the reliability of the method used for the determination of the excited state population.

Sep 1, 20080 citations

Energy transfer in collisions between two Cs(5D) atoms

Yifan Shen

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+6S7F+6S is also dicussed.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+6S7F+6S is also dicussed.

Journal of Atomic and Molecular PhysicsJan 1, 20070 citations

Excitation-transfer collisions in cesium vapor: Cs(5 D5/2 )+Cs(6 S1/2 )→Cs (5 D3/2 )+ Cs(6 S1/2 )

B. Keramati, Mark F. Masters, John Huennekens

We report an experimental investigation of the excitation-transfer collision Cs(5 ${D}_{5/2}$ )+Cs(6S)\ensuremath{\rightarrow}CS ((5 ${D}_{3/2}$ )+Cs(6S). The upper 5 ${D}_{5/2}$ state was excited by a cw dye laser tuned to the one-photon, quadrupole-allowed 6S\ensuremath{\rightarrow}5 ${D}_{5/2}$ 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 6 ${P}_{1/2}$ to 6 ${P}_{3/2}$ 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 6 ${P}_{3/2}$ state, and the same fluorescence ratio monitored. The 5D mixing cross section we obtain, 70 A ${\r{}}^{2}$ , is significantly larger than previous indirect determinations.We report an experimental investigation of the excitation-transfer collision Cs(5${D}_{5/2}$)+Cs(6S)\ensuremath{\rightarrow}CS ((5${D}_{3/2}$)+Cs(6S). The upper 5${D}_{5/2}$ state was excited by a cw dye laser tuned to the one-photon, quadrupole-allowed 6S\ensuremath{\rightarrow}5${D}_{5/2}$ 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 6${P}_{1/2}$ to 6${P}_{3/2}$ 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 6${P}_{3/2}$ state, and the same fluorescence ratio monitored. The 5D mixing cross section we obtain, 70 A${\r{}}^{2}$, is significantly larger than previous indirect determinations.

Physical Review ANov 1, 198810 citations

Energy-pooling collisions in cesium: 6{ital P}{sub {ital J}}+6{ital P}{sub {ital J}}{r_arrow}6{ital S}+({ital nl}=7{ital P},6{ital D},8{ital S},4{ital F})

Z. J. Jabbour, R. K. Namiotka, John Huennekens +3 more

We report experimental rate coefficients for the energy-pooling collisions Cs(6{ital P}{sub 1/2})+Cs(6{ital P}{sub 1/2}){r_arrow}Cs(6{ital S}{sub 1/2})+Cs({ital nl}{sub {ital J}{prime}}) and Cs(6{ital P}{sub 3/2})+Cs(6{ital P}{sub 3/2}){r_arrow}Cs(6{ital S}{sub 1/2})+Cs({ital nl}{sub {ital J}{prime}}) where {ital nl}{sub {ital J}{prime}}=7{ital P}{sub 1/2}, 7{ital P}{sub 3/2}, 6{ital D}{sub 3/2}, 6{ital D}{sub 5/2}, 8{ital S}{sub 1/2}, 4{ital F}{sub 5/2}, or 4{ital F}{sub 7/2}. Atoms were excited to either the 6{ital P}{sub 1/2} or 6{ital P}{sub 3/2} 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 6{ital P}{sub 1/2}{r_arrow}8{ital S}{sub 1/2} or 6{ital P}{sub 3/2}{r_arrow}7{ital D}{sub 3/2,5/2} 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 formore » production, in all cases, is greatest for 6{ital D}, but that 1/2-1/2 collisions are significantly more efficient than 3/2-3/2 collisions for populating 7{ital P}. It was also found that 7{ital P}{sub 1/2} is populated two to three times more efficiently than 7{ital P}{sub 3/2} in 1/2-1/2 collisions, but that the 7{ital P} fine-structure levels are approximately equally populated in 3/2-3/2 collisions. {copyright} {ital 1996 The American Physical Society.}« lessWe report experimental rate coefficients for the energy-pooling collisions Cs(6{ital P}{sub 1/2})+Cs(6{ital P}{sub 1/2}){r_arrow}Cs(6{ital S}{sub 1/2})+Cs({ital nl}{sub {ital J}{prime}}) and Cs(6{ital P}{sub 3/2})+Cs(6{ital P}{sub 3/2}){r_arrow}Cs(6{ital S}{sub 1/2})+Cs({ital nl}{sub {ital J}{prime}}) where {ital nl}{sub {ital J}{prime}}=7{ital P}{sub 1/2}, 7{ital P}{sub 3/2}, 6{ital D}{sub 3/2}, 6{ital D}{sub 5/2}, 8{ital S}{sub 1/2}, 4{ital F}{sub 5/2}, or 4{ital F}{sub 7/2}. Atoms were excited to either the 6{ital P}{sub 1/2} or 6{ital P}{sub 3/2} 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 6{ital P}{sub 1/2}{r_arrow}8{ital S}{sub 1/2} or 6{ital P}{sub 3/2}{r_arrow}7{ital D}{sub 3/2,5/2} 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 formore » production, in all cases, is greatest for 6{ital D}, but that 1/2-1/2 collisions are significantly more efficient than 3/2-3/2 collisions for populating 7{ital P}. It was also found that 7{ital P}{sub 1/2} is populated two to three times more efficiently than 7{ital P}{sub 3/2} in 1/2-1/2 collisions, but that the 7{ital P} fine-structure levels are approximately equally populated in 3/2-3/2 collisions. {copyright} {ital 1996 The American Physical Society.}« less

Physical Review AAug 1, 199641 citations

A two-step excitation experiment has been employed to measure the collisional rate coefficients and to study the velocity distribution of

\mathrm{Cs}(6{P}_{1∕2})

atoms that have undergone a single hyperfine state-changing collision with Ar. In addition, argon pressure broadening rates and shifts of the cesium

6{P}_{1∕2}({F}^{\ensuremath{'}})\ensuremath{\rightarrow}8{S}_{1∕2}({F}^{\ensuremath{''}})

transitions have been determined. In the experiment, a single mode, cw Ti:sapphire laser is tuned to line center of the

6{S}_{1∕2}(F=4)\ensuremath{\rightarrow}6{P}_{1∕2}

(

{F}^{\ensuremath{'}}=3

or 4) transition. Then, the frequency of a single mode cw dye laser is scanned over the

6{P}_{1∕2}\ensuremath{\rightarrow}8{S}_{1∕2}

manifold to probe the populations of the

6{P}_{1∕2}

hyperfine levels. Absorption of probe laser photons is monitored by detecting

8{S}_{1∕2}\ensuremath{\rightarrow}6{P}_{3∕2}

fluorescence. The experiment is conducted at room temperature, where the Cs density is low

(n\ensuremath{\sim}3.4\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})

, and thus the probability of a

\mathrm{Cs}\text{\ensuremath{-}}\mathrm{Cs}

collision is negligible during the

\mathrm{Cs}(6{P}_{1∕2})

radiative lifetime. The Ar pressure is varied from 0 to

1.52\phantom{\rule{0.3em}{0ex}}\mathrm{Torr}

, and

\mathrm{Cs}\text{\ensuremath{-}}\mathrm{Ar}

collisions cause population to be transferred from the directly excited

6{P}_{1∕2}({F}^{\ensuremath{'}})

level to the other

6{P}_{1∕2}

hyperfine level. The data are analyzed using a density matrix formalism to yield the rate coefficients for

\mathrm{Cs}(6{P}_{1∕2})\text{\ensuremath{-}}\mathrm{Ar}

hyperfine state-changing collisions. In addition, the one-dimensional velocity changing collision kernel for

\mathrm{Cs}(6{P}_{1∕2})

atoms prepared with

{v}_{z}=0

that undergo

{F}^{\ensuremath{'}}=3\ensuremath{\leftrightarrow}{F}^{\ensuremath{'}}=4

hyperfine state-changing collisions with argon is reported.

We report experimental rate coefficients for the energy-pooling collisions Cs(6

{\mathit{P}}_{1/2}

)+Cs(6

{\mathit{P}}_{1/2}

)\ensuremath{\rightarrow}Cs(6

{\mathit{S}}_{1/2}

)+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) and Cs(6

{\mathit{P}}_{3/2}

)+Cs(6

{\mathit{P}}_{3/2}

)\ensuremath{\rightarrow}Cs(6

{\mathit{S}}_{1/2}

)+Cs(${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$) where ${\mathit{nl}}_{\mathit{J}\ensuremath{'}}$=7

{\mathit{P}}_{1/2}

, 7

{\mathit{P}}_{3/2}

, 6

{\mathit{D}}_{3/2}

, 6

{\mathit{D}}_{5/2}

, 8

{\mathit{S}}_{1/2}

, 4

{\mathit{F}}_{5/2}

, or 4

{\mathit{F}}_{7/2}

. Atoms were excited to either the 6

{\mathit{P}}_{1/2}

or 6

{\mathit{P}}_{3/2}

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 6

{\mathit{P}}_{1/2}

\ensuremath{\rightarrow}8

{\mathit{S}}_{1/2}

or 6

{\mathit{P}}_{3/2}

\ensuremath{\rightarrow}7

{\mathit{D}}_{3/2,5/2}

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 7

{\mathit{P}}_{1/2}

is populated two to three times more efficiently than 7

{\mathit{P}}_{3/2}

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 report an experimental investigation of the excitation-transfer collision Cs(5

{D}_{5/2}

)+Cs(6S)\ensuremath{\rightarrow}CS ((5

{D}_{3/2}

)+Cs(6S). The upper 5

{D}_{5/2}

state was excited by a cw dye laser tuned to the one-photon, quadrupole-allowed 6S\ensuremath{\rightarrow}5

{D}_{5/2}

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 6

{P}_{1/2}

to 6

{P}_{3/2}

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 6

{P}_{3/2}

state, and the same fluorescence ratio monitored. The 5D mixing cross section we obtain, 70 A

{\r{}}^{2}

, is significantly larger than previous indirect determinations.