Optical pumping studies of collisional interactions

F. A. Franz

Published May 22, 1979• 0 citations

Abstract

A final scientific report is given on a project involving application of optical pumping techniques to studies of atomic collisions. Magnetic depolarization, nuclear spin efforts, collisional selection rules, surface interactions, and studies of sudden and quasi molecular collisions between alkali atoms and noble gas atoms are particularly emphasized. (Author)

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Velocity-selective optical pumping and collision effects

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Spin-exchange optical pumping of noble-gas nuclei

Thad G Walker, W. Happer

Spin-exchange optical pumping of mixtures of alkali-metal vapors and noble gases can be used to efficiently polarize the nuclei of the noble-gas atoms. Liters of noble gases at standard temperature and pressure and with nuclear spin polarizations of several tens of percent are now used in many applications. The authors describe the basic phenomena that govern the spin-exchange process and review the physics of angular momentum transfer and loss in optical pumping and spin-exchange collisions.

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Optical Pumping of Neon P23 Metastable Atoms

L. D. Schearer

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Optically pumped helium - a spin dependent probe

L. D. Schearer

In the 25 years since the first optical pumping experiments in helium were reported, there have been an astonishing variety of applications. We describe briefly the use of spin-polarized helium to measure interplanetary magnetic fields, to probe spin-dependent nuclear and atomic collisions, to investigate surface properties of materials, and to study the quantum properties of a spin-polarized Fermi system.

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Theory of spin-exchange optical pumping of 3 He and 129 Xe

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Optical pumping studies of collisional interactions

F. A. Franz

Published May 22, 1979• 0 citations

OpenAlex

Abstract

Related papers

Velocity-selective optical pumping and collision effects

C.G. Aminoff

Optical pumping performed with a quasi monochromatic laser beam in an atomic gas introduces a redistribution of Zeeman populations selectively in a single velocity class. In the limit of low pumping intensity the rate theory is valid for a description of velocity-selective optical pumping (V.S.O.P.). Well-defined atomic observables (population, orientation, alignment) and their velocity-correlated collisional relaxation can be studied. Also, a modified scheme for the detection of second order effects of optical pumping allows one to observe light shift induced signals. In particular, V.S.O.P. and its combination with modulated pumping, magnetic depolarization (level crossing), and magnetic resonance techniques provide information about the atomic collision characteristics such as collision rates and kernels for velocity-changing collisions.Optical pumping performed with a quasi monochromatic laser beam in an atomic gas introduces a redistribution of Zeeman populations selectively in a single velocity class. In the limit of low pumping intensity the rate theory is valid for a description of velocity-selective optical pumping (V.S.O.P.). Well-defined atomic observables (population, orientation, alignment) and their velocity-correlated collisional relaxation can be studied. Also, a modified scheme for the detection of second order effects of optical pumping allows one to observe light shift induced signals. In particular, V.S.O.P. and its combination with modulated pumping, magnetic depolarization (level crossing), and magnetic resonance techniques provide information about the atomic collision characteristics such as collision rates and kernels for velocity-changing collisions.

Annales de PhysiqueJan 1, 19852 citations

Spin-exchange optical pumping of noble-gas nuclei

Thad G Walker, W. Happer

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Optical Pumping of Neon P23 Metastable Atoms

L. D. Schearer

The $^{3}P_{2}$ metastable atoms of neon have been optically oriented. This represents the first case of the optical pumping of non- $S$ state atoms. The optical-pumping process is described, and depolarization cross sections for collisions with ground-state neon and ground-state helium atoms measured. The cross section for collisional depolarization with helium is 4.30 \ifmmode\pm\else\textpm\fi{} 0.22 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ , and with neon is 166 \ifmmode\pm\else\textpm\fi{} 8 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ at 300\ifmmode^\circ\else\textdegree\fi{}K. The metastable $^{3}P_{2}$ atoms of Ar and Xe have also been optically pumped. As the polarizability of the noble-gas buffer increases, the collisional depolarization cross section approaches the diffusion cross section.The $^{3}P_{2}$ metastable atoms of neon have been optically oriented. This represents the first case of the optical pumping of non-$S$ state atoms. The optical-pumping process is described, and depolarization cross sections for collisions with ground-state neon and ground-state helium atoms measured. The cross section for collisional depolarization with helium is 4.30 \ifmmode\pm\else\textpm\fi{} 0.22 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$, and with neon is 166 \ifmmode\pm\else\textpm\fi{} 8 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ at 300\ifmmode^\circ\else\textdegree\fi{}K. The metastable $^{3}P_{2}$ atoms of Ar and Xe have also been optically pumped. As the polarizability of the noble-gas buffer increases, the collisional depolarization cross section approaches the diffusion cross section.

Physical ReviewApr 5, 196926 citations

Optically pumped helium - a spin dependent probe

L. D. Schearer

Annales de PhysiqueJan 1, 198510 citations

The Physics of Spin Polarized Gases.

G. D. Cates

Over the four year period covered by this grant, we have carried out extensive research involving polarized atoms and nuclei. Using laser optical pumping, high polarizations can be produced in alkali-metal vapors. From this starting point, angular momentum can be transferred to other atoms and nuclei through several different types of spin-exchange collisions. This powerful technique enables us to study a wide variety of spin interactions and spin related phenomena. Among the systems we work with are polarized nobel gases, which display extremely long spin-relaxation times that vary from several minutes to many weeks. The use of optical pumping and spin exchange has grown enormously over the past four years.Over the four year period covered by this grant, we have carried out extensive research involving polarized atoms and nuclei. Using laser optical pumping, high polarizations can be produced in alkali-metal vapors. From this starting point, angular momentum can be transferred to other atoms and nuclei through several different types of spin-exchange collisions. This powerful technique enables us to study a wide variety of spin interactions and spin related phenomena. Among the systems we work with are polarized nobel gases, which display extremely long spin-relaxation times that vary from several minutes to many weeks. The use of optical pumping and spin exchange has grown enormously over the past four years.

Jan 2, 19930 citations

Theory of spin-exchange optical pumping of 3 He and 129 Xe

Stephan Appelt, Andrei Ben-Amar Baranga, Christopher Erickson +3 more

We present a comprehensive theory of nuclear spin polarization of ${}^{3}\mathrm{He}$ and ${}^{129}\mathrm{Xe}$ gases by spin-exchange collisions with optically pumped alkali-metal vapors. The most important physical processes considered are (1) spin-conserving spin-exchange collisions between like or unlike alkali-metal atoms; (2) spin-destroying collisions of the alkali-metal atoms with each other and with buffer-gas atoms; (3) electron-nuclear spin-exchange collisions between alkali-metal atoms and ${}^{3}\mathrm{He}$ or ${}^{129}\mathrm{Xe}$ atoms; (4) spin interactions in van der Waals molecules consisting of a Xe atom bound to an alkali-metal atom; (5) optical pumping by laser photons; (6) spatial diffusion. The static magnetic field is assumed to be small enough that the nuclear spin of the alkali-metal atom is well coupled to the electron spin and the total spin is very nearly a good quantum number. Conditions appropriate for the production of large quantities of spin-polarized ${}^{3}\mathrm{He}$ or ${}^{129}\mathrm{Xe}$ gas are assumed, namely, atmospheres of gas pressure and nearly complete quenching of the optically excited alkali-metal atoms by collisions with ${\mathrm{N}}_{2}$ or ${\mathrm{H}}_{2}$ gas. Some of the more important results of this work are as follows: (1) Most of the pumping and relaxation processes are sudden with respect to the nuclear polarization. Consequently, the steady-state population distribution of alkali-metal atoms is well described by a spin temperature, whether the rate of spin-exchange collisions between alkali-metal atoms is large or small compared to the optical pumping rate or the collisional spin-relaxation rates. (2) The population distributions that characterize the response to sudden changes in the intensity of the pumping light are not described by a spin temperature, except in the limit of very rapid spin exchange. (3) Expressions given for the radio-frequency (rf) resonance linewidths and areas can be used to make reliable estimates of the local spin polarization of the alkali-metal atoms. (4) Diffusion effects for these high-pressure conditions are mainly limited to thin layers at the cell surface and at internal resonant surfaces generated by radio-frequency magnetic fields when the static magnetic field has substantial spatial inhomogeneities. The highly localized effects of diffusion at these surfaces are described with closed-form analytic functions instead of the spatial eigenmode expansions that are appropriate for lower-pressure cells.We present a comprehensive theory of nuclear spin polarization of ${}^{3}\mathrm{He}$ and ${}^{129}\mathrm{Xe}$ gases by spin-exchange collisions with optically pumped alkali-metal vapors. The most important physical processes considered are (1) spin-conserving spin-exchange collisions between like or unlike alkali-metal atoms; (2) spin-destroying collisions of the alkali-metal atoms with each other and with buffer-gas atoms; (3) electron-nuclear spin-exchange collisions between alkali-metal atoms and ${}^{3}\mathrm{He}$ or ${}^{129}\mathrm{Xe}$ atoms; (4) spin interactions in van der Waals molecules consisting of a Xe atom bound to an alkali-metal atom; (5) optical pumping by laser photons; (6) spatial diffusion. The static magnetic field is assumed to be small enough that the nuclear spin of the alkali-metal atom is well coupled to the electron spin and the total spin is very nearly a good quantum number. Conditions appropriate for the production of large quantities of spin-polarized ${}^{3}\mathrm{He}$ or ${}^{129}\mathrm{Xe}$ gas are assumed, namely, atmospheres of gas pressure and nearly complete quenching of the optically excited alkali-metal atoms by collisions with ${\mathrm{N}}_{2}$ or ${\mathrm{H}}_{2}$ gas. Some of the more important results of this work are as follows: (1) Most of the pumping and relaxation processes are sudden with respect to the nuclear polarization. Consequently, the steady-state population distribution of alkali-metal atoms is well described by a spin temperature, whether the rate of spin-exchange collisions between alkali-metal atoms is large or small compared to the optical pumping rate or the collisional spin-relaxation rates. (2) The population distributions that characterize the response to sudden changes in the intensity of the pumping light are not described by a spin temperature, except in the limit of very rapid spin exchange. (3) Expressions given for the radio-frequency (rf) resonance linewidths and areas can be used to make reliable estimates of the local spin polarization of the alkali-metal atoms. (4) Diffusion effects for these high-pressure conditions are mainly limited to thin layers at the cell surface and at internal resonant surfaces generated by radio-frequency magnetic fields when the static magnetic field has substantial spatial inhomogeneities. The highly localized effects of diffusion at these surfaces are described with closed-form analytic functions instead of the spatial eigenmode expansions that are appropriate for lower-pressure cells.

Physical Review AAug 1, 1998443 citations

The

^{3}P_{2}

metastable atoms of neon have been optically oriented. This represents the first case of the optical pumping of non-

S

state atoms. The optical-pumping process is described, and depolarization cross sections for collisions with ground-state neon and ground-state helium atoms measured. The cross section for collisional depolarization with helium is 4.30 \ifmmode\pm\else\textpm\fi{} 0.22 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}17}$

{\mathrm{cm}}^{2}

, and with neon is 166 \ifmmode\pm\else\textpm\fi{} 8 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}17}$

{\mathrm{cm}}^{2}

at 300\ifmmode^\circ\else\textdegree\fi{}K. The metastable

^{3}P_{2}

atoms of Ar and Xe have also been optically pumped. As the polarizability of the noble-gas buffer increases, the collisional depolarization cross section approaches the diffusion cross section.

We present a comprehensive theory of nuclear spin polarization of

{}^{3}\mathrm{He}

and

{}^{129}\mathrm{Xe}

gases by spin-exchange collisions with optically pumped alkali-metal vapors. The most important physical processes considered are (1) spin-conserving spin-exchange collisions between like or unlike alkali-metal atoms; (2) spin-destroying collisions of the alkali-metal atoms with each other and with buffer-gas atoms; (3) electron-nuclear spin-exchange collisions between alkali-metal atoms and

{}^{3}\mathrm{He}

{}^{129}\mathrm{Xe}

atoms; (4) spin interactions in van der Waals molecules consisting of a Xe atom bound to an alkali-metal atom; (5) optical pumping by laser photons; (6) spatial diffusion. The static magnetic field is assumed to be small enough that the nuclear spin of the alkali-metal atom is well coupled to the electron spin and the total spin is very nearly a good quantum number. Conditions appropriate for the production of large quantities of spin-polarized

{}^{3}\mathrm{He}

{}^{129}\mathrm{Xe}

gas are assumed, namely, atmospheres of gas pressure and nearly complete quenching of the optically excited alkali-metal atoms by collisions with

{\mathrm{N}}_{2}

{\mathrm{H}}_{2}

gas. Some of the more important results of this work are as follows: (1) Most of the pumping and relaxation processes are sudden with respect to the nuclear polarization. Consequently, the steady-state population distribution of alkali-metal atoms is well described by a spin temperature, whether the rate of spin-exchange collisions between alkali-metal atoms is large or small compared to the optical pumping rate or the collisional spin-relaxation rates. (2) The population distributions that characterize the response to sudden changes in the intensity of the pumping light are not described by a spin temperature, except in the limit of very rapid spin exchange. (3) Expressions given for the radio-frequency (rf) resonance linewidths and areas can be used to make reliable estimates of the local spin polarization of the alkali-metal atoms. (4) Diffusion effects for these high-pressure conditions are mainly limited to thin layers at the cell surface and at internal resonant surfaces generated by radio-frequency magnetic fields when the static magnetic field has substantial spatial inhomogeneities. The highly localized effects of diffusion at these surfaces are described with closed-form analytic functions instead of the spatial eigenmode expansions that are appropriate for lower-pressure cells.