Physical Review Letters

Slowing Down of Rubidium-Induced Nuclear Spin Relaxation of Xe129 Gas in a Magnetic Field

Natarajan D. Bhaskar, W. Happer, Marcus Larsson, Xianghua Zeng

Published Jan 10, 1983• 42 citations

Abstract

The longitudinal relaxation rate of $^{129}\mathrm{Xe}$ nuclear spins slows down substantially in an external magnetic field of about 100 G. From an analysis of the magnetic slowing down and of the dependence of the zero-field relaxation rates on the third-body pressure, the authors have deduced the magnitudes of the spin-rotation and spin-exchange interactions in the ${\mathrm{Rb}}^{129}$Xe molecule, as well as the formation and breakup rates of RbXe in ${\mathrm{N}}_{2}$ gas and the dissociation constant of RbXe. The magnetic slowing down shows directly that binary collisions contribute no more than a few percent to the relaxation rates.

DOI: 10.1103/physrevlett.50.105

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Physical Review Letters

Slowing Down of Rubidium-Induced Nuclear Spin Relaxation of Xe129 Gas in a Magnetic Field

Natarajan D. Bhaskar, W. Happer, Marcus Larsson, Xianghua Zeng

Published Jan 10, 1983• 42 citations

Publisher

Abstract

The longitudinal relaxation rate of

^{129}\mathrm{Xe}

nuclear spins slows down substantially in an external magnetic field of about 100 G. From an analysis of the magnetic slowing down and of the dependence of the zero-field relaxation rates on the third-body pressure, the authors have deduced the magnitudes of the spin-rotation and spin-exchange interactions in the

{\mathrm{Rb}}^{129}

Xe molecule, as well as the formation and breakup rates of RbXe in

{\mathrm{N}}_{2}

gas and the dissociation constant of RbXe. The magnetic slowing down shows directly that binary collisions contribute no more than a few percent to the relaxation rates.

DOI: 10.1103/physrevlett.50.105

Related papers

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 $\ensuremath{\kappa}{=d(1/T}_{1})/d[\mathrm{Rb}]=(1.75\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{s}.$

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The experimental determination of the nuclear spin relaxation of129Xe

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Measurement of Xe129−Cs binary spin-exchange rate coefficient

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

We report the first measurement of the spin-exchange rate coefficient for binary collisions between Cs and $^{129}\mathrm{Xe}$ atoms in the temperature range $110<T<150\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ at a $9.4\text{\ensuremath{-}}\mathrm{T}$ magnetic field. Under these conditions, binary spin-exchange collisions dominate the longitudinal nuclear spin-relaxation rate $1∕{T}_{1}$ of $^{129}\mathrm{Xe}$ gas. We measured $1∕{T}_{1}$ of a thermally polarized Xe gas using the saturation-recovery of conventional nuclear magnetic resonance. We also directly measured the Cs atomic number density [Cs] by using Faraday rotation of the linear polarization of a probing laser beam passing through the sample. The measured rate coefficient is $\ensuremath{\kappa}(9.4\phantom{\rule{0.3em}{0ex}}\mathrm{T})=d(1∕{T}_{1})∕d[\mathrm{Cs}]=(2.81\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}∕\mathrm{s}$, which is about a factor of 1.6 higher than the previously measured spin-exchange rate coefficient of $^{129}\mathrm{Xe}\text{\ensuremath{-}}\mathrm{Rb}$ binary collisions. Using a calculated magnetic decoupling factor, we extrapolate our result to zero magnetic field: $\ensuremath{\kappa}(0\phantom{\rule{0.3em}{0ex}}\mathrm{T})=(4.1\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}∕\mathrm{s}$.We report the first measurement of the spin-exchange rate coefficient for binary collisions between Cs and $^{129}\mathrm{Xe}$ atoms in the temperature range $110<T<150\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ at a $9.4\text{\ensuremath{-}}\mathrm{T}$ magnetic field. Under these conditions, binary spin-exchange collisions dominate the longitudinal nuclear spin-relaxation rate $1∕{T}_{1}$ of $^{129}\mathrm{Xe}$ gas. We measured $1∕{T}_{1}$ of a thermally polarized Xe gas using the saturation-recovery of conventional nuclear magnetic resonance. We also directly measured the Cs atomic number density [Cs] by using Faraday rotation of the linear polarization of a probing laser beam passing through the sample. The measured rate coefficient is $\ensuremath{\kappa}(9.4\phantom{\rule{0.3em}{0ex}}\mathrm{T})=d(1∕{T}_{1})∕d[\mathrm{Cs}]=(2.81\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}∕\mathrm{s}$, which is about a factor of 1.6 higher than the previously measured spin-exchange rate coefficient of $^{129}\mathrm{Xe}\text{\ensuremath{-}}\mathrm{Rb}$ binary collisions. Using a calculated magnetic decoupling factor, we extrapolate our result to zero magnetic field: $\ensuremath{\kappa}(0\phantom{\rule{0.3em}{0ex}}\mathrm{T})=(4.1\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}∕\mathrm{s}$.

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Rb-Xe spin relaxation in dilute Xe mixtures

Ian A. Nelson, Thad G Walker

We present measurements of spin-relaxation of Rb atoms in $\mathrm{He}(98%)\ensuremath{-}{\mathrm{N}}_{2}(1%)\ensuremath{-}\mathrm{Xe}(1%)$ mixtures similar to those used in magnetic resonance imaging polarizers. The pressure dependence allows us to separate out contributions from Rb-Xe van der Waals molecules and binary collisions. For the first time, we observe the predicted increase in the molecular contribution at high pressure. Our data suggest that the deduced molecular breakup rate has a strong temperature dependence.We present measurements of spin-relaxation of Rb atoms in $\mathrm{He}(98%)\ensuremath{-}{\mathrm{N}}_{2}(1%)\ensuremath{-}\mathrm{Xe}(1%)$ mixtures similar to those used in magnetic resonance imaging polarizers. The pressure dependence allows us to separate out contributions from Rb-Xe van der Waals molecules and binary collisions. For the first time, we observe the predicted increase in the molecular contribution at high pressure. Our data suggest that the deduced molecular breakup rate has a strong temperature dependence.

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Measurement of the nuclear spin relaxation of 131 Xe in 87 Rb atoms

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Magnetic decoupling of 129Xe−Rb and 129Xe−Cs binary spin exchange

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

We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of ${}^{129}\mathrm{Xe}$ atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb},$ where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of ${}^{129}\mathrm{Xe}$ atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb},$ where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.

Physical Review AFeb 28, 200323 citations

The longitudinal relaxation rate of

^{129}\mathrm{Xe}

{\mathrm{Rb}}^{129}

Xe molecule, as well as the formation and breakup rates of RbXe in

{\mathrm{N}}_{2}

gas and the dissociation constant of RbXe. The magnetic slowing down shows directly that binary collisions contribute no more than a few percent to the relaxation rates.

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 $\ensuremath{\kappa}{=d(1/T}_{1})/d[\mathrm{Rb}]=(1.75\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{3}/\mathrm{s}.$

We report the first measurement of the spin-exchange rate coefficient for binary collisions between Cs and

^{129}\mathrm{Xe}

atoms in the temperature range $110<T<150\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ at a $9.4\text{\ensuremath{-}}\mathrm{T}$ magnetic field. Under these conditions, binary spin-exchange collisions dominate the longitudinal nuclear spin-relaxation rate

1∕{T}_{1}

^{129}\mathrm{Xe}

gas. We measured

1∕{T}_{1}

of a thermally polarized Xe gas using the saturation-recovery of conventional nuclear magnetic resonance. We also directly measured the Cs atomic number density [Cs] by using Faraday rotation of the linear polarization of a probing laser beam passing through the sample. The measured rate coefficient is $\ensuremath{\kappa}(9.4\phantom{\rule{0.3em}{0ex}}\mathrm{T})=d(1∕{T}_{1})∕d[\mathrm{Cs}]=(2.81\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}∕\mathrm{s}$, which is about a factor of 1.6 higher than the previously measured spin-exchange rate coefficient of $^{129}\mathrm{Xe}\text{\ensuremath{-}}\mathrm{Rb}$ binary collisions. Using a calculated magnetic decoupling factor, we extrapolate our result to zero magnetic field: $\ensuremath{\kappa}(0\phantom{\rule{0.3em}{0ex}}\mathrm{T})=(4.1\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}∕\mathrm{s}$.

We present measurements of spin-relaxation of Rb atoms in

\mathrm{He}(98%)\ensuremath{-}{\mathrm{N}}_{2}(1%)\ensuremath{-}\mathrm{Xe}(1%)

mixtures similar to those used in magnetic resonance imaging polarizers. The pressure dependence allows us to separate out contributions from Rb-Xe van der Waals molecules and binary collisions. For the first time, we observe the predicted increase in the molecular contribution at high pressure. Our data suggest that the deduced molecular breakup rate has a strong temperature dependence.

We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of

{}^{129}\mathrm{Xe}

atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb},$ where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.