Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Spin-polarization dependence of the Rb-Xe spin-exchange optical pumping process

Bowen Song, Yanhua Wang, Nan Zhao

Published Aug 17, 2021• 20 citations
Publisher

Abstract

We experimentally study the Rb-Xe spin-exchange optical pumping process. The dependence of the spin-exchange rate on the intensity of the pumping light is measured at different temperatures under low magnetic fields. We demonstrate that the spin-exchange rate will decrease as the Rb spin polarization increases, which agrees well with the theoretical prediction. In our measurement, three spin exchange and spin relaxation mechanisms, namely, the spin exchange rates between Rb and Xe atoms caused by van der Waals molecule (${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{vdW}}$) and binary collision (${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{bin}}$) processes, and the spin relaxation rate due to the wall collision of Xe atoms (${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{w}}$), have comparable magnitudes. These rates are extracted separately from the measured data with different Rb spin polarization at various temperatures. Our work provides a comprehensive confirmation of the physical picture of the spin-exchange optical pumping process.

DOI
10.1103/physreva.104.023105

Related papers

Rubidium–xenon spin exchange and relaxation rates measured at high pressure and high magnetic field

Charles V. Rice, Daniel Raftery

The production of hyperpolarized Xe via spin exchange with optically pumped Rb atoms was studied at 47 000 G under high-pressure conditions. From variable pressure and temperature studies, the spin exchange efficiency was found to be pressure dependent and lower than comparable low-field measurements. Spin exchange due to short binary collisions is expected to be pressure independent, and the cross section was measured to be 〈σν〉SE=6.0 (±0.1)×10−17 cm3 s−1. The pressure dependent component was attributed to the formation of Rb–Xe van der Waals (vdW) complexes. The rate constant for spin exchange in Rb–Xe vdW complexes was measured to be κ=1400 (±100) s−1 in He buffer gas. This value is comparable, though somewhat smaller than vdW rates measured previously for other buffer gases. While it is well known that spin exchange occurs readily in vdW complexes when B0<200 G, vdW spin exchange at fields >10 000 G is not accounted for in current theories. Modulation of the hyperfine interaction during the vdW complex lifetime is proposed to account for these observations. Finally, relaxation by the walls of the pumping cell was found to increase with buffer gas pressure. These factors impact the equilibrium Xe polarization obtainable with high-field optical pumping.

The Journal of Chemical Physics•Sep 5, 2002•23 citations

Polarization transfer in a spin-exchange optical-pumping experiment

Jyrki Rantaharju, Matti Hanni, Juha Vaara

Spin-exchange optical pumping (SEOP) enables hyperpolarization of magnetic noble gas nuclei and allows enormously enhanced signal in nuclear magnetic resonance studies in materials, biosciences, and medicine. We model the dynamics of the SEOP process taking place in a $\mathrm{Rb}\ensuremath{-}^{129}\mathrm{Xe}$ gas mixture and shed light on how the different microscopic processes influence the macroscopic polarization transfer. For each Rb-Xe collision taking place in simulated molecular dynamics trajectory, we sample a time series of quantum-chemically preparametrized Hamiltonians. Combined electron and nuclear spin dynamics of each event is propagated by solving the corresponding Liouville--von Neumann equation. The rarely occurring, long-lived van der Waals molecules are seen to give the most significant contribution to polarization transfer under the simulated conditions ($T=300$ K, $p=2.4$ bar), in agreement with earlier findings. Besides the lifetime of the collision complex, the average and minimum Rb-Xe interatomic distances characterize the efficiency of the polarization transfer events. We obtain insight into magnetization transfer in both individual binary collisions and van der Waals complexes and demonstrate a stepwise buildup of $^{129}\mathrm{Xe}$ spin polarization upon bond-length oscillations in the latter.

Physical Review A•Sep 14, 2020•5 citations

Comparative spin-exchange efficiency of Rb– 129 Xe and Cs– 129 Xe in the long-lived van der Waals regime: implications for high-throughput 129 Xe hyperpolarization

Tao shi, Ge Jin, Liu Bowen +4 more

Abstract Efficient production of hyperpolarized 129 Xe at clinically relevant output levels remains an important challenge for spin-exchange optical pumping (SEOP). In this work, we report a comparative experimental study of Cs– 129 Xe and Rb– 129 Xe SEOP. The spin-exchange and spin-relaxation rates are measured and separated into binary-collision and van der Waals (vdW) molecular contributions. The resulting parameter set shows that long-lived vdW interactions enhance the intrinsic spin-exchange efficiency within a narrow pressure window, with Cs exhibiting a modest advantage over Rb under comparable conditions. Using these experimentally constrained quantities in a device-level model, we predict that clinically relevant 129 Xe polarization levels and throughput could be achievable at pump powers near 5 W.

Journal of Physics D Applied Physics•Jun 23, 2026•0 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 $\ensuremath{\kappa}{=d(1/T}_{1})/d[\mathrm{Rb}]=(1.75\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{s}.$

Physical Review A•Nov 15, 2002•40 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.

Physical Review A•Aug 1, 1998•443 citations

Rb − 129 Xe spin-exchange rates due to binary and three-body collisions at high Xe pressures

G. D. Cates, R. J. Fitzgerald, A. S. Barton +4 more

We have studied the spin relaxation of $^{129}\mathrm{Xe}$ nuclei due to collisions with Rb atoms at Xe pressures of 245--1817 Torr. Our results can be characterized by two parameters, the Rb${\mathrm{\ensuremath{-}}}^{129}$Xe velocity-averaged binary spin-exchange cross section 〈\ensuremath{\sigma}v〉 and a rate ${\ensuremath{\gamma}}_{\mathit{M}}$ that characterizes spin relaxation due to van der Waals molecules. Our results complement earlier studies performed at Xe pressures of about 1 Torr and ${\mathrm{N}}_{2}$ pressures of 10--100 Torr. This work is useful for predicting spin-exchange rates between polarized Rb atoms and $^{129}\mathrm{Xe}$ nuclei.

Physical Review A•Apr 1, 1992•107 citations
We experimentally study the Rb-Xe spin-exchange optical pumping process. The dependence of the spin-exchange rate on the intensity of the pumping light is measured at different temperatures under low magnetic fields. We demonstrate that the spin-exchange rate will decrease as the Rb spin polarization increases, which agrees well with the theoretical prediction. In our measurement, three spin exchange and spin relaxation mechanisms, namely, the spin exchange rates between Rb and Xe atoms caused by van der Waals molecule (\ensuremathΓvdW{\mathrm{\ensuremath{\Gamma}}}_{\mathrm{vdW}}\ensuremathΓvdW​) and binary collision (\ensuremathΓbin{\mathrm{\ensuremath{\Gamma}}}_{\mathrm{bin}}\ensuremathΓbin​) processes, and the spin relaxation rate due to the wall collision of Xe atoms (\ensuremathΓw{\mathrm{\ensuremath{\Gamma}}}_{\mathrm{w}}\ensuremathΓw​), have comparable magnitudes. These rates are extracted separately from the measured data with different Rb spin polarization at various temperatures. Our work provides a comprehensive confirmation of the physical picture of the spin-exchange optical pumping process.
The production of hyperpolarized Xe via spin exchange with optically pumped Rb atoms was studied at 47 000 G under high-pressure conditions. From variable pressure and temperature studies, the spin exchange efficiency was found to be pressure dependent and lower than comparable low-field measurements. Spin exchange due to short binary collisions is expected to be pressure independent, and the cross section was measured to be 〈σν〉SE=6.0 (±0.1)×10−17 cm3 s−1. The pressure dependent component was attributed to the formation of Rb–Xe van der Waals (vdW) complexes. The rate constant for spin exchange in Rb–Xe vdW complexes was measured to be κ=1400 (±100) s−1 in He buffer gas. This value is comparable, though somewhat smaller than vdW rates measured previously for other buffer gases. While it is well known that spin exchange occurs readily in vdW complexes when B0<200 G, vdW spin exchange at fields >10 000 G is not accounted for in current theories. Modulation of the hyperfine interaction during the vdW complex lifetime is proposed to account for these observations. Finally, relaxation by the walls of the pumping cell was found to increase with buffer gas pressure. These factors impact the equilibrium Xe polarization obtainable with high-field optical pumping.
Spin-exchange optical pumping (SEOP) enables hyperpolarization of magnetic noble gas nuclei and allows enormously enhanced signal in nuclear magnetic resonance studies in materials, biosciences, and medicine. We model the dynamics of the SEOP process taking place in a $\mathrm{Rb}\ensuremath{-}^{129}\mathrm{Xe}$ gas mixture and shed light on how the different microscopic processes influence the macroscopic polarization transfer. For each Rb-Xe collision taking place in simulated molecular dynamics trajectory, we sample a time series of quantum-chemically preparametrized Hamiltonians. Combined electron and nuclear spin dynamics of each event is propagated by solving the corresponding Liouville--von Neumann equation. The rarely occurring, long-lived van der Waals molecules are seen to give the most significant contribution to polarization transfer under the simulated conditions (T=300T=300T=300 K, p=2.4p=2.4p=2.4 bar), in agreement with earlier findings. Besides the lifetime of the collision complex, the average and minimum Rb-Xe interatomic distances characterize the efficiency of the polarization transfer events. We obtain insight into magnetization transfer in both individual binary collisions and van der Waals complexes and demonstrate a stepwise buildup of 129Xe^{129}\mathrm{Xe}129Xe spin polarization upon bond-length oscillations in the latter.
Abstract Efficient production of hyperpolarized 129 Xe at clinically relevant output levels remains an important challenge for spin-exchange optical pumping (SEOP). In this work, we report a comparative experimental study of Cs– 129 Xe and Rb– 129 Xe SEOP. The spin-exchange and spin-relaxation rates are measured and separated into binary-collision and van der Waals (vdW) molecular contributions. The resulting parameter set shows that long-lived vdW interactions enhance the intrinsic spin-exchange efficiency within a narrow pressure window, with Cs exhibiting a modest advantage over Rb under comparable conditions. Using these experimentally constrained quantities in a device-level model, we predict that clinically relevant 129 Xe polarization levels and throughput could be achievable at pump powers near 5 W.
We have measured the binary spin-exchange rate coefficient for collisions between Rb and 129Xe{}^{129}\mathrm{Xe}129Xe atoms at a magnetic field B=9.4TB=9.4\mathrm{T}B=9.4T and in the temperature range $160<T<200\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The longitudinal spin-relaxation rate 1/T1{1/T}_{1}1/T1​ of 129Xe{}^{129}\mathrm{Xe}129Xe is dominated by ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ binary collisions. We measured 1/T1{1/T}_{1}1/T1​ 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 present a comprehensive theory of nuclear spin polarization of 3He{}^{3}\mathrm{He}3He and 129Xe{}^{129}\mathrm{Xe}129Xe 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 3He{}^{3}\mathrm{He}3He or 129Xe{}^{129}\mathrm{Xe}129Xe 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 3He{}^{3}\mathrm{He}3He or 129Xe{}^{129}\mathrm{Xe}129Xe gas are assumed, namely, atmospheres of gas pressure and nearly complete quenching of the optically excited alkali-metal atoms by collisions with N2{\mathrm{N}}_{2}N2​ or H2{\mathrm{H}}_{2}H2​ 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 studied the spin relaxation of 129Xe^{129}\mathrm{Xe}129Xe nuclei due to collisions with Rb atoms at Xe pressures of 245--1817 Torr. Our results can be characterized by two parameters, the Rb${\mathrm{\ensuremath{-}}}^{129}$Xe velocity-averaged binary spin-exchange cross section 〈\ensuremath{\sigma}v〉 and a rate ${\ensuremath{\gamma}}_{\mathit{M}}$ that characterizes spin relaxation due to van der Waals molecules. Our results complement earlier studies performed at Xe pressures of about 1 Torr and N2{\mathrm{N}}_{2}N2​ pressures of 10--100 Torr. This work is useful for predicting spin-exchange rates between polarized Rb atoms and 129Xe^{129}\mathrm{Xe}129Xe nuclei.