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Physical Review

Collisional Depolarization of the Rb 5p and Cs 6p Doublets

Alan C. Gallagher

Published May 5, 1967• 90 citations
Publisher

Abstract

Using the Hanle-effect technique, the cross sections for collisional depolarization of the Rb $^{2}P_{\frac{1}{2},\frac{3}{2}}$ and Cs $^{2}P_{\frac{1}{2}}$ states by inert-gas collisions have been measured. (The natural lifetimes of these states were also obtained from the measurements.) The $^{2}P_{\frac{1}{2}}$-state depolarization cross sections are much smaller than any previously reported for $L\ensuremath{\ne}0$ states. This results from a strong selection rule governing nonresonant collisions. This selection rule is derived and its effect on $J=\frac{1}{2}$-state depolarization is demonstrated. A relationship between the reported cross sections and sensitized fluorescence cross sections is noted.

DOI
10.1103/physrev.157.68

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Collisional Depolarization of the Rb 5p and Cs 6p Doublets

Alan C. Gallagher

Using the Hanle-effect technique, the cross sections for collisional depolarization of the Rb $^{2}P_{\frac{1}{2},\frac{3}{2}}$ and Cs $^{2}P_{\frac{1}{2}}$ states by inert-gas collisions have been measured. (The natural lifetimes of these states were also obtained from the measurements.) The $^{2}P_{\frac{1}{2}}$-state depolarization cross sections are much smaller than any previously reported for $L\ensuremath{\ne}0$ states. This results from a strong selection rule governing nonresonant collisions. This selection rule is derived and its effect on $J=\frac{1}{2}$-state depolarization is demonstrated. A relationship between the reported cross sections and sensitized fluorescence cross sections is noted.

Physical Review•Nov 5, 1967•11 citations

Measurement of the collisional depolarization cross section of the silver 5P122 state by helium

M. Soltanolkotabr, R. Gupta

We have measured the cross section for depolarization of the $5^{2}P_{\frac{1}{2}}$ state of silver atoms by collisions with helium atoms using the Hanle-effect technique. We find the nuclear-spin-independent cross section to be $\ensuremath{\sigma}=1.2\ifmmode\pm\else\textpm\fi{}0.15\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$, significantly smaller than the corresponding cross sections in rubidium and cesium. This is the first measurement of this quantity in any noble-metal atom.

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

A. C. Tam, T. Yabuzaki, Stephen M. Curry +2 more

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.

Physical Review A•Jun 1, 1978•29 citations

Depolarization of 6P322 cesium atoms, induced in collisions with noble gases

J. Guiry, L. Krause

Cross sections for relaxation of circular and linear polarization of $6^{2}P_{\frac{3}{2}}$ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-\AA{} Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ is coupled to the electronic angular momentum $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$, the measurements yielded depolarization cross sections $Q(\mathrm{circ}.)$ and $Q(\mathrm{lin}.)$, which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.

Physical Review A•Dec 1, 1976•13 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.

Physical Review•Jan 5, 1967•41 citations

Collisional relaxation in 5(2)P potassium atoms.

R. W. Berends

Collisional excitation transfer and relaxation of K 5$\\sp2$P atoms in collisions with noble gases, as well as the radiative lifetimes of the K 5P, 6P and 7P fine-structure states have been investigated by methods of atomic fluorescence spectroscopy. Potassium vapour was mixed in a cell with a noble gas and selectively excited by pulsed dye-laser radiation to the 5$\\sp2$P$\\sb{1\\over2}$ or the 5$\\sp2$P$\\sb{3\\over 2}$ state in zero magnetic field and to the 5$\\sp2$P$\\sb{{1\\over 2}-{1\\over 2}}$ or the 5$\\sp2$P$\\sb{{3\\over 2}-{3\\over 2}}$ Zeeman substate in a field of 70 kG. Interferometric analysis of the fluorescence emitted from the directly (optically) excited state and that emitted from the collisionally populated states allowed the determination of the fine-structure mixing cross sections for collisions with He, Ne, Ar, Kr and Xe in zero magnetic field. Excitation transfer between Zeeman substates was investigated for collisions between the selectively excited 5P atoms and He, Ne and Ar atoms, allowing the determination of the multipole relaxation (depolarization) cross sections for dipole, quadrupole and octupole decay, as well as the Zeeman and fine-structure mixing cross sections and orientation transfer cross sections. A comparison of theoretical calculations with the experimental data has been made and the rate equations governing multipole relaxation and including effects due to strong fine-structure mixing on the multipole relaxation, have been described in detail. The radiative lifetimes of the individual fine-structure components of the K 5P, 6P and 7P states have been determined experimentally by means of time-resolved laser-induced fluorescence techniques. These data are compared with numerous theoretical calculations and the available experimental values.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1988 .B474. Source: Dissertation Abstracts International, Volume: 49-04, Section: B, page: 1223. Thesis (Ph.D.)--University of Windsor (Canada), 1988.

•Jan 1, 1988•0 citations
Using the Hanle-effect technique, the cross sections for collisional depolarization of the Rb 2P12,32^{2}P_{\frac{1}{2},\frac{3}{2}}2P21​,23​​ and Cs 2P12^{2}P_{\frac{1}{2}}2P21​​ states by inert-gas collisions have been measured. (The natural lifetimes of these states were also obtained from the measurements.) The 2P12^{2}P_{\frac{1}{2}}2P21​​-state depolarization cross sections are much smaller than any previously reported for L\ensuremath≠0L\ensuremath{\ne}0L\ensuremath=0 states. This results from a strong selection rule governing nonresonant collisions. This selection rule is derived and its effect on J=12J=\frac{1}{2}J=21​-state depolarization is demonstrated. A relationship between the reported cross sections and sensitized fluorescence cross sections is noted.
Using the Hanle-effect technique, the cross sections for collisional depolarization of the Rb 2P12,32^{2}P_{\frac{1}{2},\frac{3}{2}}2P21​,23​​ and Cs 2P12^{2}P_{\frac{1}{2}}2P21​​ states by inert-gas collisions have been measured. (The natural lifetimes of these states were also obtained from the measurements.) The 2P12^{2}P_{\frac{1}{2}}2P21​​-state depolarization cross sections are much smaller than any previously reported for $L\ensuremath{\ne}0$ states. This results from a strong selection rule governing nonresonant collisions. This selection rule is derived and its effect on J=12J=\frac{1}{2}J=21​-state depolarization is demonstrated. A relationship between the reported cross sections and sensitized fluorescence cross sections is noted.
We have measured the cross section for depolarization of the 52P125^{2}P_{\frac{1}{2}}52P21​​ state of silver atoms by collisions with helium atoms using the Hanle-effect technique. We find the nuclear-spin-independent cross section to be $\ensuremath{\sigma}=1.2\ifmmode\pm\else\textpm\fi{}0.15\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ cm2{\mathrm{cm}}^{2}cm2, significantly smaller than the corresponding cross sections in rubidium and cesium. This is the first measurement of this quantity in any noble-metal atom.
The inelastic collisional cross sections of the nD\mathrm{nD}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 ${10}^{\ensuremath{-}14}$ cm2{\mathrm{cm}}^{2}cm2) 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 nnn 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 ${10}^{\ensuremath{-}14}$ cm2{\mathrm{cm}}^{2}cm2) for excitation transfer out of the nD\mathrm{nD}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 nnn 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 nD\mathrm{nD}nD states studied, except 6D6D6D, whose fine-structure-changing cross section is unusually large.
Cross sections for relaxation of circular and linear polarization of 62P326^{2}P_{\frac{3}{2}}62P23​​ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-\AA{} Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ is coupled to the electronic angular momentum $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$, the measurements yielded depolarization cross sections Q(circ.)Q(\mathrm{circ}.)Q(circ.) and Q(lin.)Q(\mathrm{lin}.)Q(lin.), which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.
Excitation transfer between the 62P126 ^{2}P_{\frac{1}{2}}62P21​​ and 62P326 ^{2}P_{\frac{3}{2}}62P23​​ resonance states in cesium, induced by Cs-N2{\mathrm{N}}_{2}N2​ and Cs-H2{\mathrm{H}}_{2}H2​ 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-N2{\mathrm{N}}_{2}N2​ collisions: ${Q}_{12}(^{2}P_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}P_{\frac{3}{2}})=3.6$ A˚2{\mathrm{\AA{}}}^{2}A˚2, ${Q}_{21}(^{2}P_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=16.2$ A˚2{\mathrm{\AA{}}}^{2}A˚2, ${Q}_{10}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{1}{2}})=55.2$ A˚2{\mathrm{\AA{}}}^{2}A˚2, ${Q}_{20}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=63.5$ A˚2{\mathrm{\AA{}}}^{2}A˚2. For Cs-H2{\mathrm{H}}_{2}H2​ collisions: Q12=6.7{Q}_{12}=6.7Q12​=6.7 A˚2{\mathrm{\AA{}}}^{2}A˚2, Q21=29.6{Q}_{21}=29.6Q21​=29.6 A˚2{\mathrm{\AA{}}}^{2}A˚2, Q10=11.7{Q}_{10}=11.7Q10​=11.7 A˚2{\mathrm{\AA{}}}^{2}A˚2, Q20=6.7{Q}_{20}=6.7Q20​=6.7 A˚2{\mathrm{\AA{}}}^{2}A˚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.
Collisional excitation transfer and relaxation of K 5sp2\\sp2sp2P atoms in collisions with noble gases, as well as the radiative lifetimes of the K 5P, 6P and 7P fine-structure states have been investigated by methods of atomic fluorescence spectroscopy. Potassium vapour was mixed in a cell with a noble gas and selectively excited by pulsed dye-laser radiation to the 5sp2\\sp2sp2Psb1over2\\sb{1\\over2}sb1over2 or the 5sp2\\sp2sp2Psb3over2\\sb{3\\over 2}sb3over2 state in zero magnetic field and to the 5sp2\\sp2sp2Psb1over2−1over2\\sb{{1\\over 2}-{1\\over 2}}sb1over2−1over2 or the 5sp2\\sp2sp2Psb3over2−3over2\\sb{{3\\over 2}-{3\\over 2}}sb3over2−3over2 Zeeman substate in a field of 70 kG. Interferometric analysis of the fluorescence emitted from the directly (optically) excited state and that emitted from the collisionally populated states allowed the determination of the fine-structure mixing cross sections for collisions with He, Ne, Ar, Kr and Xe in zero magnetic field. Excitation transfer between Zeeman substates was investigated for collisions between the selectively excited 5P atoms and He, Ne and Ar atoms, allowing the determination of the multipole relaxation (depolarization) cross sections for dipole, quadrupole and octupole decay, as well as the Zeeman and fine-structure mixing cross sections and orientation transfer cross sections. A comparison of theoretical calculations with the experimental data has been made and the rate equations governing multipole relaxation and including effects due to strong fine-structure mixing on the multipole relaxation, have been described in detail. The radiative lifetimes of the individual fine-structure components of the K 5P, 6P and 7P states have been determined experimentally by means of time-resolved laser-induced fluorescence techniques. These data are compared with numerous theoretical calculations and the available experimental values.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1988 .B474. Source: Dissertation Abstracts International, Volume: 49-04, Section: B, page: 1223. Thesis (Ph.D.)--University of Windsor (Canada), 1988.