Physical Review Letters

Polarization of Ne21 by Spin Exchange with Optically Pumped Rb Vapor

T. E. Chupp, K. P. Coulter

Published Sep 2, 1985• 38 citations

Abstract

We report investigations of spin exchange between $^{21}\mathrm{Ne}$ nuclei and optically pumped Rb vapor. Polarization of 30% ($〈{K}_{z}〉=0.46$) of 2\ifmmode\times\else\texttimes\fi{}${10}^{19}$ atoms-${\mathrm{cm}}^{\ensuremath{-}3}$ has been achieved with a vapor pressure of 3\ifmmode\times\else\texttimes\fi{}${10}^{14}$ atoms-${\mathrm{cm}}^{\ensuremath{-}3}$ of Rb. This high density of alkali metal can be efficiently optically pumped only when light trapping is suppressed by inclusion of at least 100 Torr of ${\mathrm{N}}_{2}$. In addition, we have made the first accurate measurement of the binary-collision spin-exchange rate: $〈{\ensuremath{\sigma}}_{\mathrm{ex}}v〉=(4.66\ifmmode\pm\else\textpm\fi{}0.28)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}$ ${\mathrm{cm}}^{3}$-${\mathrm{s}}^{\ensuremath{-}1}$. Extension of these techniques to $^{3}\mathrm{He}$ has yielded 5% polarization of 2\ifmmode\times\else\texttimes\fi{}${10}^{19}$ atoms-${\mathrm{cm}}^{\ensuremath{-}3}$ in a preliminary experiment.

DOI: 10.1103/physrevlett.55.1074

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Polarization of 3He by Spin Exchange with Optically Pumped Rb and K Vapors

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Production of a nuclear-spin-polarized Ne21 sample

B. C. Grover

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High-field measurement of the 129Xe−Rb spin-exchange rate due to binary collisions

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Physical Review Letters

Polarization of Ne21 by Spin Exchange with Optically Pumped Rb Vapor

T. E. Chupp, K. P. Coulter

Published Sep 2, 1985• 38 citations

Publisher

Abstract

We report investigations of spin exchange between

^{21}\mathrm{Ne}

nuclei and optically pumped Rb vapor. Polarization of 30% (

〈{K}_{z}〉=0.46

) of 2\ifmmode\times\else\texttimes\fi{}

{10}^{19}

atoms-

{\mathrm{cm}}^{\ensuremath{-}3}

has been achieved with a vapor pressure of 3\ifmmode\times\else\texttimes\fi{}

{10}^{14}

atoms-

{\mathrm{cm}}^{\ensuremath{-}3}

of Rb. This high density of alkali metal can be efficiently optically pumped only when light trapping is suppressed by inclusion of at least 100 Torr of

{\mathrm{N}}_{2}

. In addition, we have made the first accurate measurement of the binary-collision spin-exchange rate:

〈{\ensuremath{\sigma}}_{\mathrm{ex}}v〉=(4.66\ifmmode\pm\else\textpm\fi{}0.28)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}

{\mathrm{cm}}^{3}

{\mathrm{s}}^{\ensuremath{-}1}

. Extension of these techniques to

^{3}\mathrm{He}

has yielded 5% polarization of 2\ifmmode\times\else\texttimes\fi{}

{10}^{19}

atoms-

{\mathrm{cm}}^{\ensuremath{-}3}

in a preliminary experiment.

DOI: 10.1103/physrevlett.55.1074

Related papers

Polarization of 3He by Spin Exchange with Optically Pumped Rb and K Vapors

Andrei Ben-Amar Baranga, Stephan Appelt, Michael V. Romalis +4 more

We report on extensive experimental measurements of the key rates that determine the efficiency for polarizing the nuclei of ${}^{3}\mathrm{He}$ by spin exchange with optically pumped Rb vapor. In agreement with recent theoretical predictions, we find a strong temperature dependence of the electron-spin loss rates due to ${}^{3}\mathrm{HeRb}$ collisions. We also find that the maximum possible efficiency for spin-exchange polarization of ${}^{3}\mathrm{He}$ by K is 10 times greater than for Rb.We report on extensive experimental measurements of the key rates that determine the efficiency for polarizing the nuclei of ${}^{3}\mathrm{He}$ by spin exchange with optically pumped Rb vapor. In agreement with recent theoretical predictions, we find a strong temperature dependence of the electron-spin loss rates due to ${}^{3}\mathrm{HeRb}$ collisions. We also find that the maximum possible efficiency for spin-exchange polarization of ${}^{3}\mathrm{He}$ by K is 10 times greater than for Rb.

Physical Review LettersMar 30, 1998118 citations

Production of a nuclear-spin-polarized Ne21 sample

B. C. Grover

Nuclear-spin-polarized samples of up to 200 Torr $^{21}\mathrm{Ne}$ have been obtained through spin-exchange collisions with optically pumped Rb vapor. The exponential time constant associated with buildup and decay of this polarization along the quantization axis is in excess of 15 h in 3-cm-diam Pyrex cells. From the data and estimates given, samples of $^{21}\mathrm{Ne}$ with densities greater than 1 STP and polarization in excess of 1% appear feasible.Nuclear-spin-polarized samples of up to 200 Torr $^{21}\mathrm{Ne}$ have been obtained through spin-exchange collisions with optically pumped Rb vapor. The exponential time constant associated with buildup and decay of this polarization along the quantization axis is in excess of 15 h in 3-cm-diam Pyrex cells. From the data and estimates given, samples of $^{21}\mathrm{Ne}$ with densities greater than 1 STP and polarization in excess of 1% appear feasible.

Physical Review AOct 1, 19836 citations

Optical pumping of Rb in the presence of high-pressure He3 buffer gas

B. Larson, O. Häusser, P. P. J. Delheij +2 more

A cryogenic technique has been used to produce polarized $^{3}\mathrm{He}$ targets of up to relative density p=12 atm (\ensuremath{\approxeq}3\ifmmode\times\else\texttimes\fi{} ${10}^{20}$ $^{3}\mathrm{He}$ atoms/ ${\mathrm{cm}}^{3}$ ; p=1 atm corresponds to 760 Torr or 101.3 kPa pressure at 273 K). In these targets $^{3}\mathrm{He}$ nuclei are polarized by spin-exchange collisions with optically pumped rubidium atoms. From transmission measurements at wavelengths of 790--800 nm, we have determined pressure shifts, linewidths, and line-shape asymmetries for the Rb 5 ${\mathit{S}}_{1/2}$ \ensuremath{\rightarrow}5 ${\mathit{P}}_{1/2}$ D1 transition. The Rb spin-destruction rate was found to exhibit a quadratic increase versus $^{3}\mathrm{He}$ pressure, which indicates the importance of Rb${\mathrm{\ensuremath{-}}}^{3}$He${\mathrm{\ensuremath{-}}}^{3}$He collision processes. The transmission results for circularly polarized light are well described by a model that predicts the dependence of the average Rb polarization on Rb density, $^{3}\mathrm{He}$ pressure, light intensity, and cell geometry. The Rb${\mathrm{\ensuremath{-}}}^{3}$He spin-exchange cross section, 〈${\mathrm{\ensuremath{\sigma}}}_{\mathrm{SE}}$v〉=6.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}20}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, was found to be independent of $^{3}\mathrm{He}$ pressure up to p=12.1 atm. Maximum $^{3}\mathrm{He}$ polarizations of 72--79% were observed with cells of 17 ${\mathrm{cm}}^{3}$ volume that contained $^{3}\mathrm{He}$ at p=6--9 atm.A cryogenic technique has been used to produce polarized $^{3}\mathrm{He}$ targets of up to relative density p=12 atm (\ensuremath{\approxeq}3\ifmmode\times\else\texttimes\fi{}${10}^{20}$ $^{3}\mathrm{He}$ atoms/${\mathrm{cm}}^{3}$; p=1 atm corresponds to 760 Torr or 101.3 kPa pressure at 273 K). In these targets $^{3}\mathrm{He}$ nuclei are polarized by spin-exchange collisions with optically pumped rubidium atoms. From transmission measurements at wavelengths of 790--800 nm, we have determined pressure shifts, linewidths, and line-shape asymmetries for the Rb 5${\mathit{S}}_{1/2}$\ensuremath{\rightarrow}5${\mathit{P}}_{1/2}$ D1 transition. The Rb spin-destruction rate was found to exhibit a quadratic increase versus $^{3}\mathrm{He}$ pressure, which indicates the importance of Rb${\mathrm{\ensuremath{-}}}^{3}$He${\mathrm{\ensuremath{-}}}^{3}$He collision processes. The transmission results for circularly polarized light are well described by a model that predicts the dependence of the average Rb polarization on Rb density, $^{3}\mathrm{He}$ pressure, light intensity, and cell geometry. The Rb${\mathrm{\ensuremath{-}}}^{3}$He spin-exchange cross section, 〈${\mathrm{\ensuremath{\sigma}}}_{\mathrm{SE}}$v〉=6.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}20}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, was found to be independent of $^{3}\mathrm{He}$ pressure up to p=12.1 atm. Maximum $^{3}\mathrm{He}$ polarizations of 72--79% were observed with cells of 17 ${\mathrm{cm}}^{3}$ volume that contained $^{3}\mathrm{He}$ at p=6--9 atm.

Physical Review ASep 1, 199180 citations

Hybrid Spin-Exchange Optical Pumping of H e 3

Earl Babcock, Ian A. Nelson, Steve Kadlecek +4 more

We demonstrate spin-exchange optical pumping of $^{3}\mathrm{H}\mathrm{e}$ using a ``hybrid'' K-Rb vapor mixture. The Rb atoms absorb light from a standard laser at 795 nm, then collisionally polarize the potassium atoms. Spin-exchange collisions of K and $^{3}\mathrm{H}\mathrm{e}$ atoms then transfer the angular momentum to the $^{3}\mathrm{H}\mathrm{e}$ with much greater efficiency than $\mathrm{R}\mathrm{b}\mathrm{\text{\ensuremath{-}}}^{3}\mathrm{H}\mathrm{e}$. For a K-rich vapor, the efficiency of the hybrid spin-exchange collisions approaches $1/4$ , an order of magnitude greater than achieved by pure Rb pumping. We present the first measurements of actual photon efficiencies (polarized nuclei produced per absorbed photon), and show that a new parasitic absorption process limits the total efficiencies for both hybrid and pure Rb pumping.We demonstrate spin-exchange optical pumping of $^{3}\mathrm{H}\mathrm{e}$ using a ``hybrid'' K-Rb vapor mixture. The Rb atoms absorb light from a standard laser at 795 nm, then collisionally polarize the potassium atoms. Spin-exchange collisions of K and $^{3}\mathrm{H}\mathrm{e}$ atoms then transfer the angular momentum to the $^{3}\mathrm{H}\mathrm{e}$ with much greater efficiency than $\mathrm{R}\mathrm{b}\mathrm{\text{\ensuremath{-}}}^{3}\mathrm{H}\mathrm{e}$. For a K-rich vapor, the efficiency of the hybrid spin-exchange collisions approaches $1/4$, an order of magnitude greater than achieved by pure Rb pumping. We present the first measurements of actual photon efficiencies (polarized nuclei produced per absorbed photon), and show that a new parasitic absorption process limits the total efficiencies for both hybrid and pure Rb pumping.

Physical Review LettersSep 16, 2003233 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

High-field measurement of the 129Xe−Rb spin-exchange rate due to binary collisions

Yuan‐Yu Jau, Nicholas N. Kuzma, W. Happer

We have measured the binary spin-exchange rate coefficient for collisions between Rb and ${}^{129}\mathrm{Xe}$ atoms at a magnetic field $B=9.4\mathrm{T}$ and in the temperature range $160<T<200\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The longitudinal spin-relaxation rate ${1/T}_{1}$ of ${}^{129}\mathrm{Xe}$ is dominated by ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ binary collisions. We measured ${1/T}_{1}$ using the methods of conventional nuclear magnetic resonance, with no spin enhancement by optical pumping. At the high magnetic field and large gas pressures used in this work, the contribution of ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ molecules to the spin-exchange rate was less than 0.1% of the binary-collision rate. The Rb atomic number density [Rb] was measured directly from the large Faraday rotation of the polarization of near-resonant light passing through the sample cells. The rate coefficient is $\ensuremath{\kappa}{=d(1/T}_{1})/d[\mathrm{Rb}]=(1.75\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{s}.$We have measured the binary spin-exchange rate coefficient for collisions between Rb and ${}^{129}\mathrm{Xe}$ atoms at a magnetic field $B=9.4\mathrm{T}$ and in the temperature range $160<T<200\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The longitudinal spin-relaxation rate ${1/T}_{1}$ of ${}^{129}\mathrm{Xe}$ is dominated by ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ binary collisions. We measured ${1/T}_{1}$ using the methods of conventional nuclear magnetic resonance, with no spin enhancement by optical pumping. At the high magnetic field and large gas pressures used in this work, the contribution of ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ molecules to the spin-exchange rate was less than 0.1% of the binary-collision rate. The Rb atomic number density [Rb] was measured directly from the large Faraday rotation of the polarization of near-resonant light passing through the sample cells. The rate coefficient is $\ensuremath{\kappa}{=d(1/T}_{1})/d[\mathrm{Rb}]=(1.75\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{s}.$

Physical Review ANov 15, 200240 citations

We report investigations of spin exchange between

^{21}\mathrm{Ne}

nuclei and optically pumped Rb vapor. Polarization of 30% (

〈{K}_{z}〉=0.46

) of 2\ifmmode\times\else\texttimes\fi{}

{10}^{19}

atoms-

{\mathrm{cm}}^{\ensuremath{-}3}

has been achieved with a vapor pressure of 3\ifmmode\times\else\texttimes\fi{}

{10}^{14}

atoms-

{\mathrm{cm}}^{\ensuremath{-}3}

of Rb. This high density of alkali metal can be efficiently optically pumped only when light trapping is suppressed by inclusion of at least 100 Torr of

{\mathrm{N}}_{2}

. In addition, we have made the first accurate measurement of the binary-collision spin-exchange rate:

〈{\ensuremath{\sigma}}_{\mathrm{ex}}v〉=(4.66\ifmmode\pm\else\textpm\fi{}0.28)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}

{\mathrm{cm}}^{3}

{\mathrm{s}}^{\ensuremath{-}1}

. Extension of these techniques to

^{3}\mathrm{He}

has yielded 5% polarization of 2\ifmmode\times\else\texttimes\fi{}

{10}^{19}

atoms-

{\mathrm{cm}}^{\ensuremath{-}3}

in a preliminary experiment.

We report on extensive experimental measurements of the key rates that determine the efficiency for polarizing the nuclei of

{}^{3}\mathrm{He}

by spin exchange with optically pumped Rb vapor. In agreement with recent theoretical predictions, we find a strong temperature dependence of the electron-spin loss rates due to

{}^{3}\mathrm{HeRb}

collisions. We also find that the maximum possible efficiency for spin-exchange polarization of

{}^{3}\mathrm{He}

by K is 10 times greater than for Rb.

Nuclear-spin-polarized samples of up to 200 Torr

^{21}\mathrm{Ne}

have been obtained through spin-exchange collisions with optically pumped Rb vapor. The exponential time constant associated with buildup and decay of this polarization along the quantization axis is in excess of 15 h in 3-cm-diam Pyrex cells. From the data and estimates given, samples of

^{21}\mathrm{Ne}

with densities greater than 1 STP and polarization in excess of 1% appear feasible.

A cryogenic technique has been used to produce polarized

^{3}\mathrm{He}

targets of up to relative density p=12 atm (\ensuremath{\approxeq}3\ifmmode\times\else\texttimes\fi{}

{10}^{20}

^{3}\mathrm{He}

atoms/

{\mathrm{cm}}^{3}

; p=1 atm corresponds to 760 Torr or 101.3 kPa pressure at 273 K). In these targets

^{3}\mathrm{He}

nuclei are polarized by spin-exchange collisions with optically pumped rubidium atoms. From transmission measurements at wavelengths of 790--800 nm, we have determined pressure shifts, linewidths, and line-shape asymmetries for the Rb 5

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

\ensuremath{\rightarrow}5

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

D1 transition. The Rb spin-destruction rate was found to exhibit a quadratic increase versus

^{3}\mathrm{He}

pressure, which indicates the importance of Rb${\mathrm{\ensuremath{-}}}^{3}$He${\mathrm{\ensuremath{-}}}^{3}$He collision processes. The transmission results for circularly polarized light are well described by a model that predicts the dependence of the average Rb polarization on Rb density,

^{3}\mathrm{He}

pressure, light intensity, and cell geometry. The Rb${\mathrm{\ensuremath{-}}}^{3}$He spin-exchange cross section, 〈${\mathrm{\ensuremath{\sigma}}}_{\mathrm{SE}}$v〉=6.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}20}$

{\mathrm{cm}}^{3}

${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, was found to be independent of

^{3}\mathrm{He}

pressure up to p=12.1 atm. Maximum

^{3}\mathrm{He}

polarizations of 72--79% were observed with cells of 17

{\mathrm{cm}}^{3}

volume that contained

^{3}\mathrm{He}

at p=6--9 atm.

We demonstrate spin-exchange optical pumping of

^{3}\mathrm{H}\mathrm{e}

using a ``hybrid'' K-Rb vapor mixture. The Rb atoms absorb light from a standard laser at 795 nm, then collisionally polarize the potassium atoms. Spin-exchange collisions of K and

^{3}\mathrm{H}\mathrm{e}

atoms then transfer the angular momentum to the

^{3}\mathrm{H}\mathrm{e}

with much greater efficiency than $\mathrm{R}\mathrm{b}\mathrm{\text{\ensuremath{-}}}^{3}\mathrm{H}\mathrm{e}$. For a K-rich vapor, the efficiency of the hybrid spin-exchange collisions approaches

1/4

, an order of magnitude greater than achieved by pure Rb pumping. We present the first measurements of actual photon efficiencies (polarized nuclei produced per absorbed photon), and show that a new parasitic absorption process limits the total efficiencies for both hybrid and pure Rb pumping.

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.

We have measured the binary spin-exchange rate coefficient for collisions between Rb and

{}^{129}\mathrm{Xe}

atoms at a magnetic field

B=9.4\mathrm{T}

and in the temperature range $160<T<200\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The longitudinal spin-relaxation rate

{1/T}_{1}

{}^{129}\mathrm{Xe}

is dominated by ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ binary collisions. We measured

{1/T}_{1}

using the methods of conventional nuclear magnetic resonance, with no spin enhancement by optical pumping. At the high magnetic field and large gas pressures used in this work, the contribution of ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ molecules to the spin-exchange rate was less than 0.1% of the binary-collision rate. The Rb atomic number density [Rb] was measured directly from the large Faraday rotation of the polarization of near-resonant light passing through the sample cells. The rate coefficient is $\ensuremath{\kappa}{=d(1/T}_{1})/d[\mathrm{Rb}]=(1.75\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{s}.$