Physical Review A

Inelastic cross sections in Cs(nDJ2)+Cs(6S122) collisions

A. C. Tam, T. Yabuzaki, Stephen M. Curry, M. Hou, W. Happer

Published Jun 1, 1978• 29 citations

Abstract

The inelastic collisional cross sections of the $\mathrm{nD}$ states of Cs are measured by the technique of selective laser excitation and observation of collision-induced fluorescence. The cross sections (in units of ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$) for the fine-structure-changing collisions [i.e., $\mathrm{Cs}(n^{2}D_{\frac{3}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Cs}(n^{2}D_{\frac{5}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})$] for $n$ being 6-10 are 2.7\ifmmode\pm\else\textpm\fi{}0.5, 3.7\ifmmode\pm\else\textpm\fi{}0.7, 8.6\ifmmode\pm\else\textpm\fi{}1.7, 18.4\ifmmode\pm\else\textpm\fi{}3.7, and 29.8\ifmmode\pm\else\textpm\fi{}6.0, respectively. The cross sections (in ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$) for excitation transfer out of the $\mathrm{nD}$ doublet [i.e., $\mathrm{Cs}(n^{2}D_{\frac{5}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than} \mathrm{Cs}(\mathrm{nD})$] for $n$ being 6-10 are 1.1\ifmmode\pm\else\textpm\fi{}0.6, 5.3\ifmmode\pm\else\textpm\fi{}1.5, 3.6\ifmmode\pm\else\textpm\fi{}1.5, 6.3\ifmmode\pm\else\textpm\fi{}2.3, and 15.5\ifmmode\pm\else\textpm\fi{}4.0, respectively. The fine-structure-changing cross sections are found to be nearly equal to the geometrical cross section $\ensuremath{\pi}{n}^{*4}{a}_{0}^{2}$ for all the $\mathrm{nD}$ states studied, except $6D$, whose fine-structure-changing cross section is unusually large.

DOI: 10.1103/physreva.17.1862

Related papers

Fine-structure mixing in Cs atoms excited to intermediate nD5/2states colliding with ground-state Cs atoms

Leszek Sirko, K. Rosiński

The collisional excitation transfer fine-structure mixing cross sections for nD states of Cs (n=11-13) are measured by the technique of selective two-photon excitation with pulses of radiation from a N 2 laser-pumped dye laser and observation of collisionally induced fluorescence.

Journal of Physics B Atomic and Molecular PhysicsApr 28, 198516 citations

Fine-structure-changing collision cross sections within the low-lying nD2 states of rubidium induced by ground-state rubidium atoms

Joel Wm. Parker, Hans A. Schuessler, R. H. Hill +1 more

Physical Review AFeb 1, 198421 citations

Inelastic collisions between selectively excited rubidium atoms and ground-state rubidium atoms

R. H. Hill, Hans A. Schuessler, Byron George Zollars

Physical Review AFeb 1, 198210 citations

Inelastic collisions between selectively excited rubidium 6D2 -state atoms and noble-gas atoms: Fine-structure-state mixing

Byron George Zollars, Hans A. Schuessler, Joel Wm. Parker +1 more

Physical Review ASep 1, 19839 citations

[Experimental evaluation of the cross sections in Cs (6D(1/2)) + Cs(6S(1/2)) inelastic collisions].

Qi-cun Guo, Hongping Wu, Li-kui Kang +3 more

Sep 1, 20090 citations

Inelastic Collisions between Excited Alkali Atoms and Molecules. I. Sensitized Fluorescence and Quenching in Cs- N2 and Cs- H2 Systems

D. A. McGillis, L. Krause

Physical ReviewJan 5, 196741 citations

Physical Review A

Inelastic cross sections in Cs(nDJ2)+Cs(6S122) collisions

A. C. Tam, T. Yabuzaki, Stephen M. Curry, M. Hou, W. Happer

Published Jun 1, 1978• 29 citations

Publisher

Abstract

The inelastic collisional cross sections of the

\mathrm{nD}

states of Cs are measured by the technique of selective laser excitation and observation of collision-induced fluorescence. The cross sections (in units of

{10}^{\ensuremath{-}14}

{\mathrm{cm}}^{2}

) for the fine-structure-changing collisions [i.e.,

\mathrm{Cs}(n^{2}D_{\frac{3}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Cs}(n^{2}D_{\frac{5}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})

] for

n

being 6-10 are 2.7\ifmmode\pm\else\textpm\fi{}0.5, 3.7\ifmmode\pm\else\textpm\fi{}0.7, 8.6\ifmmode\pm\else\textpm\fi{}1.7, 18.4\ifmmode\pm\else\textpm\fi{}3.7, and 29.8\ifmmode\pm\else\textpm\fi{}6.0, respectively. The cross sections (in

{10}^{\ensuremath{-}14}

{\mathrm{cm}}^{2}

) for excitation transfer out of the

\mathrm{nD}

doublet [i.e.,

\mathrm{Cs}(n^{2}D_{\frac{5}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than} \mathrm{Cs}(\mathrm{nD})

] for

n

being 6-10 are 1.1\ifmmode\pm\else\textpm\fi{}0.6, 5.3\ifmmode\pm\else\textpm\fi{}1.5, 3.6\ifmmode\pm\else\textpm\fi{}1.5, 6.3\ifmmode\pm\else\textpm\fi{}2.3, and 15.5\ifmmode\pm\else\textpm\fi{}4.0, respectively. The fine-structure-changing cross sections are found to be nearly equal to the geometrical cross section

\ensuremath{\pi}{n}^{*4}{a}_{0}^{2}

for all the

\mathrm{nD}

states studied, except

6D

, whose fine-structure-changing cross section is unusually large.

DOI: 10.1103/physreva.17.1862

Related papers

Fine-structure mixing in Cs atoms excited to intermediate nD5/2states colliding with ground-state Cs atoms

Leszek Sirko, K. Rosiński

Journal of Physics B Atomic and Molecular PhysicsApr 28, 198516 citations

Fine-structure-changing collision cross sections within the low-lying nD2 states of rubidium induced by ground-state rubidium atoms

Joel Wm. Parker, Hans A. Schuessler, R. H. Hill +1 more

The thermal cross sections for inelastic transfer of excited rubidium atoms from the $n^{2}D_{\frac{5}{2}}$ to the $n^{2}D_{\frac{3}{2}}$ fine-structure state caused by fine-structure-changing collisions with ground-state rubidium atoms have been measured by selective stepwise excitation of the rubidium atoms and observation of the resulting fluorescence. The cross sections (in units of ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$ ) for $n$ being 5-9 are 2.9\ifmmode\pm\else\textpm\fi{}0.6, 6.9\ifmmode\pm\else\textpm\fi{}1.4, 11.5\ifmmode\pm\else\textpm\fi{}2.3, 17.1\ifmmode\pm\else\textpm\fi{}3.0, and 26.0\ifmmode\pm\else\textpm\fi{}5.0, respectively. The fine-structure-changing cross sections are of the order of the geometrical cross sections and increase slightly less than ${({n}^{*})}^{4}$ for the low-lying $n^{2}D$ states studied.The thermal cross sections for inelastic transfer of excited rubidium atoms from the $n^{2}D_{\frac{5}{2}}$ to the $n^{2}D_{\frac{3}{2}}$ fine-structure state caused by fine-structure-changing collisions with ground-state rubidium atoms have been measured by selective stepwise excitation of the rubidium atoms and observation of the resulting fluorescence. The cross sections (in units of ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$) for $n$ being 5-9 are 2.9\ifmmode\pm\else\textpm\fi{}0.6, 6.9\ifmmode\pm\else\textpm\fi{}1.4, 11.5\ifmmode\pm\else\textpm\fi{}2.3, 17.1\ifmmode\pm\else\textpm\fi{}3.0, and 26.0\ifmmode\pm\else\textpm\fi{}5.0, respectively. The fine-structure-changing cross sections are of the order of the geometrical cross sections and increase slightly less than ${({n}^{*})}^{4}$ for the low-lying $n^{2}D$ states studied.

Physical Review AFeb 1, 198421 citations

Inelastic collisions between selectively excited rubidium atoms and ground-state rubidium atoms

R. H. Hill, Hans A. Schuessler, Byron George Zollars

Inelastic-collision processes in fine-structure-changing collisions have been studied by selective stepwise excitation and observation of the resulting fluorescence. Hereby, the effect of ground-state rubidium atoms colliding with excited-state rubidium atoms was investigated. The ground-state density was changed by three orders of magnitude by performing the measurements over the temperature range of 75 to 200 \ifmmode^\circ\else\textdegree\fi{}C. The cross section for fine-structure-changing collisions [i.e., $\mathrm{Rb}({6}^{2}{D}_{\frac{5}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Rb}({6}^{2}{D}_{\frac{3}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})$] is ${\ensuremath{\sigma}}_{\mathrm{fs}}=(1.0\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{2}$ . The cross sections for transfer out of the fine-structure doublet [i.e., $\mathrm{Rb}({6}^{2}D)+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than}\mathrm{Rb}({6}^{2}D)$] is ${\ensuremath{\sigma}}_{\mathrm{tr}}=(3.8\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{2}$ . It is demonstrated that for the intermediate excited rubidium states, both the fine-structure-changing and transfer cross sections are of the order of the geometrical cross section of the excited rubidium states.Inelastic-collision processes in fine-structure-changing collisions have been studied by selective stepwise excitation and observation of the resulting fluorescence. Hereby, the effect of ground-state rubidium atoms colliding with excited-state rubidium atoms was investigated. The ground-state density was changed by three orders of magnitude by performing the measurements over the temperature range of 75 to 200 \ifmmode^\circ\else\textdegree\fi{}C. The cross section for fine-structure-changing collisions [i.e., $\mathrm{Rb}({6}^{2}{D}_{\frac{5}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Rb}({6}^{2}{D}_{\frac{3}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})$] is ${\ensuremath{\sigma}}_{\mathrm{fs}}=(1.0\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{2}$. The cross sections for transfer out of the fine-structure doublet [i.e., $\mathrm{Rb}({6}^{2}D)+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than}\mathrm{Rb}({6}^{2}D)$] is ${\ensuremath{\sigma}}_{\mathrm{tr}}=(3.8\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{2}$. It is demonstrated that for the intermediate excited rubidium states, both the fine-structure-changing and transfer cross sections are of the order of the geometrical cross section of the excited rubidium states.

Physical Review AFeb 1, 198210 citations

Inelastic collisions between selectively excited rubidium 6D2 -state atoms and noble-gas atoms: Fine-structure-state mixing

Byron George Zollars, Hans A. Schuessler, Joel Wm. Parker +1 more

Inelastic collisional processes in fine-structure-state mixing have been studied by selective stepwise excitation and observation of the resulting fluorescence during collisions of excited rubidium $6^{2}D_{\frac{5}{2}}$ state atoms with various noble-gas atoms. It is shown that for intermediately excited rubidium atoms the fine-structure-state mixing cross sections are generally increasing from helium to xexon. The cross sections for the process $\mathrm{Rb}(6^{2}D_{\frac{5}{2}})+A(n^{1}S_{0})\ensuremath{\rightarrow}\mathrm{Rb}(6^{2}D_{\frac{3}{2}})+A(n^{1}S_{0})+\ensuremath{\Delta}E$ have the values ${\ensuremath{\sigma}}_{\mathrm{fs}}^{*}=2.4\ifmmode\pm\else\textpm\fi{}0.9, 3.1\ifmmode\pm\else\textpm\fi{}1.2, 2.6\ifmmode\pm\else\textpm\fi{}1.0, 5.8\ifmmode\pm\else\textpm\fi{}2.2, \mathrm{and} 9.3\ifmmode\pm\else\textpm\fi{}5.6$ in units of ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$ , where $A$ denotes in sequence any one of the noble gas atoms He, Ne, Ar, Kr, and Xe, respectively. Transfer cross sections for the transfer of excited Rb $6^{2}D$ -state atoms out of the doublet were also determined and are about an order of magnitude smaller than the fine-structure-mixing cross sections.Inelastic collisional processes in fine-structure-state mixing have been studied by selective stepwise excitation and observation of the resulting fluorescence during collisions of excited rubidium $6^{2}D_{\frac{5}{2}}$ state atoms with various noble-gas atoms. It is shown that for intermediately excited rubidium atoms the fine-structure-state mixing cross sections are generally increasing from helium to xexon. The cross sections for the process $\mathrm{Rb}(6^{2}D_{\frac{5}{2}})+A(n^{1}S_{0})\ensuremath{\rightarrow}\mathrm{Rb}(6^{2}D_{\frac{3}{2}})+A(n^{1}S_{0})+\ensuremath{\Delta}E$ have the values ${\ensuremath{\sigma}}_{\mathrm{fs}}^{*}=2.4\ifmmode\pm\else\textpm\fi{}0.9, 3.1\ifmmode\pm\else\textpm\fi{}1.2, 2.6\ifmmode\pm\else\textpm\fi{}1.0, 5.8\ifmmode\pm\else\textpm\fi{}2.2, \mathrm{and} 9.3\ifmmode\pm\else\textpm\fi{}5.6$ in units of ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$, where $A$ denotes in sequence any one of the noble gas atoms He, Ne, Ar, Kr, and Xe, respectively. Transfer cross sections for the transfer of excited Rb$6^{2}D$-state atoms out of the doublet were also determined and are about an order of magnitude smaller than the fine-structure-mixing cross sections.

Physical Review ASep 1, 19839 citations

[Experimental evaluation of the cross sections in Cs (6D(1/2)) + Cs(6S(1/2)) inelastic collisions].

Qi-cun Guo, Hongping Wu, Li-kui Kang +3 more

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.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.

Sep 1, 20090 citations

Inelastic Collisions between Excited Alkali Atoms and Molecules. I. Sensitized Fluorescence and Quenching in Cs- N2 and Cs- H2 Systems

D. A. McGillis, L. Krause

Excitation transfer between the $6 ^{2}P_{\frac{1}{2}}$ and $6 ^{2}P_{\frac{3}{2}}$ resonance states in cesium, induced by Cs- ${\mathrm{N}}_{2}$ and Cs- ${\mathrm{H}}_{2}$ collisions, was observed in the first experiment of its kind, in which techniques of sensitized fluorescence are used to investigate collisional mixing between resonance states of alkali atoms in mixtures with molecular gases. The cesium-vapor-gas system, in which the cesium vapor pressure was low enough to avoid radiation trapping, was irradiated with a single component of the resonance doublet. The fluorescent light, which contained both components of the doublet, was monitored at right angles to the direction of excitation. Measurements of relative intensities of the fluorescent components yielded the following cross sections for excitation transfer and for quenching of resonance radiation. For Cs- ${\mathrm{N}}_{2}$ collisions: ${Q}_{12}(^{2}P_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}P_{\frac{3}{2}})=3.6$ ${\mathrm{\AA{}}}^{2}$ , ${Q}_{21}(^{2}P_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=16.2$ ${\mathrm{\AA{}}}^{2}$ , ${Q}_{10}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{1}{2}})=55.2$ ${\mathrm{\AA{}}}^{2}$ , ${Q}_{20}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=63.5$ ${\mathrm{\AA{}}}^{2}$ . For Cs- ${\mathrm{H}}_{2}$ collisions: ${Q}_{12}=6.7$ ${\mathrm{\AA{}}}^{2}$ , ${Q}_{21}=29.6$ ${\mathrm{\AA{}}}^{2}$ , ${Q}_{10}=11.7$ ${\mathrm{\AA{}}}^{2}$ , ${Q}_{20}=6.7$ ${\mathrm{\AA{}}}^{2}$ . The large sizes of the excitation-transfer cross sections, which are comparable to the corresponding Cs-Cs cross sections, are attributed to resonances with transitions in the molecules.Excitation transfer between the $6 ^{2}P_{\frac{1}{2}}$ and $6 ^{2}P_{\frac{3}{2}}$ resonance states in cesium, induced by Cs-${\mathrm{N}}_{2}$ and Cs-${\mathrm{H}}_{2}$ collisions, was observed in the first experiment of its kind, in which techniques of sensitized fluorescence are used to investigate collisional mixing between resonance states of alkali atoms in mixtures with molecular gases. The cesium-vapor-gas system, in which the cesium vapor pressure was low enough to avoid radiation trapping, was irradiated with a single component of the resonance doublet. The fluorescent light, which contained both components of the doublet, was monitored at right angles to the direction of excitation. Measurements of relative intensities of the fluorescent components yielded the following cross sections for excitation transfer and for quenching of resonance radiation. For Cs-${\mathrm{N}}_{2}$ collisions: ${Q}_{12}(^{2}P_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}P_{\frac{3}{2}})=3.6$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{21}(^{2}P_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=16.2$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{10}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{1}{2}})=55.2$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{20}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=63.5$ ${\mathrm{\AA{}}}^{2}$. For Cs-${\mathrm{H}}_{2}$ collisions: ${Q}_{12}=6.7$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{21}=29.6$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{10}=11.7$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{20}=6.7$ ${\mathrm{\AA{}}}^{2}$. The large sizes of the excitation-transfer cross sections, which are comparable to the corresponding Cs-Cs cross sections, are attributed to resonances with transitions in the molecules.

Physical ReviewJan 5, 196741 citations

The inelastic collisional cross sections of the

\mathrm{nD}

states of Cs are measured by the technique of selective laser excitation and observation of collision-induced fluorescence. The cross sections (in units of

{10}^{\ensuremath{-}14}

{\mathrm{cm}}^{2}

) for the fine-structure-changing collisions [i.e.,

\mathrm{Cs}(n^{2}D_{\frac{3}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Cs}(n^{2}D_{\frac{5}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})

] for

n

{10}^{\ensuremath{-}14}

{\mathrm{cm}}^{2}

) for excitation transfer out of the

\mathrm{nD}

doublet [i.e.,

\mathrm{Cs}(n^{2}D_{\frac{5}{2}})+\mathrm{Cs}(6^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than} \mathrm{Cs}(\mathrm{nD})

] for

n

\ensuremath{\pi}{n}^{*4}{a}_{0}^{2}

for all the

\mathrm{nD}

states studied, except

6D

, whose fine-structure-changing cross section is unusually large.

The thermal cross sections for inelastic transfer of excited rubidium atoms from the

n^{2}D_{\frac{5}{2}}

to the

n^{2}D_{\frac{3}{2}}

fine-structure state caused by fine-structure-changing collisions with ground-state rubidium atoms have been measured by selective stepwise excitation of the rubidium atoms and observation of the resulting fluorescence. The cross sections (in units of ${10}^{\ensuremath{-}14}$

{\mathrm{cm}}^{2}

) for

n

being 5-9 are 2.9\ifmmode\pm\else\textpm\fi{}0.6, 6.9\ifmmode\pm\else\textpm\fi{}1.4, 11.5\ifmmode\pm\else\textpm\fi{}2.3, 17.1\ifmmode\pm\else\textpm\fi{}3.0, and 26.0\ifmmode\pm\else\textpm\fi{}5.0, respectively. The fine-structure-changing cross sections are of the order of the geometrical cross sections and increase slightly less than

{({n}^{*})}^{4}

for the low-lying

n^{2}D

states studied.

{\mathrm{cm}}^{2}

. The cross sections for transfer out of the fine-structure doublet [i.e., $\mathrm{Rb}({6}^{2}D)+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than}\mathrm{Rb}({6}^{2}D)$] is ${\ensuremath{\sigma}}_{\mathrm{tr}}=(3.8\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$

{\mathrm{cm}}^{2}

. It is demonstrated that for the intermediate excited rubidium states, both the fine-structure-changing and transfer cross sections are of the order of the geometrical cross section of the excited rubidium states.

Inelastic collisional processes in fine-structure-state mixing have been studied by selective stepwise excitation and observation of the resulting fluorescence during collisions of excited rubidium

6^{2}D_{\frac{5}{2}}

state atoms with various noble-gas atoms. It is shown that for intermediately excited rubidium atoms the fine-structure-state mixing cross sections are generally increasing from helium to xexon. The cross sections for the process $\mathrm{Rb}(6^{2}D_{\frac{5}{2}})+A(n^{1}S_{0})\ensuremath{\rightarrow}\mathrm{Rb}(6^{2}D_{\frac{3}{2}})+A(n^{1}S_{0})+\ensuremath{\Delta}E$ have the values ${\ensuremath{\sigma}}_{\mathrm{fs}}^{*}=2.4\ifmmode\pm\else\textpm\fi{}0.9, 3.1\ifmmode\pm\else\textpm\fi{}1.2, 2.6\ifmmode\pm\else\textpm\fi{}1.0, 5.8\ifmmode\pm\else\textpm\fi{}2.2, \mathrm{and} 9.3\ifmmode\pm\else\textpm\fi{}5.6$ in units of ${10}^{\ensuremath{-}14}$

{\mathrm{cm}}^{2}

, where

A

denotes in sequence any one of the noble gas atoms He, Ne, Ar, Kr, and Xe, respectively. Transfer cross sections for the transfer of excited Rb

6^{2}D

-state atoms out of the doublet were also determined and are about an order of magnitude smaller than the fine-structure-mixing cross sections.

Excitation transfer between the

6 ^{2}P_{\frac{1}{2}}

and

6 ^{2}P_{\frac{3}{2}}

resonance states in cesium, induced by Cs-

{\mathrm{N}}_{2}

and Cs-

{\mathrm{H}}_{2}

collisions, was observed in the first experiment of its kind, in which techniques of sensitized fluorescence are used to investigate collisional mixing between resonance states of alkali atoms in mixtures with molecular gases. The cesium-vapor-gas system, in which the cesium vapor pressure was low enough to avoid radiation trapping, was irradiated with a single component of the resonance doublet. The fluorescent light, which contained both components of the doublet, was monitored at right angles to the direction of excitation. Measurements of relative intensities of the fluorescent components yielded the following cross sections for excitation transfer and for quenching of resonance radiation. For Cs-

{\mathrm{N}}_{2}

collisions: ${Q}_{12}(^{2}P_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}P_{\frac{3}{2}})=3.6$

{\mathrm{\AA{}}}^{2}

, ${Q}_{21}(^{2}P_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=16.2$

{\mathrm{\AA{}}}^{2}

, ${Q}_{10}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{1}{2}})=55.2$

{\mathrm{\AA{}}}^{2}

, ${Q}_{20}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=63.5$

{\mathrm{\AA{}}}^{2}

. For Cs-

{\mathrm{H}}_{2}

collisions:

{Q}_{12}=6.7

{\mathrm{\AA{}}}^{2}

{Q}_{21}=29.6

{\mathrm{\AA{}}}^{2}

{Q}_{10}=11.7

{\mathrm{\AA{}}}^{2}

{Q}_{20}=6.7

{\mathrm{\AA{}}}^{2}

. The large sizes of the excitation-transfer cross sections, which are comparable to the corresponding Cs-Cs cross sections, are attributed to resonances with transitions in the molecules.