A Measurement of the Spin Relaxation Time of Optically Pumped Rubidium Vapor

We have produced highly spin-polarized atomic hydrogen by spin-exchange optical pumping. A tunable ring dye laser is used to polarize rubidium atoms by optical pumping. The cell containing the rubidium vapor is coated with paraffin in order to reduce spin relaxation due to wall collisions. Hydrogen gas is dissociated in an inductive discharge and flows continuously through the cell, in which the hydrogen atoms are polarized by spin-exchange collisions with the polarized rubidium atoms. Atomic-hydrogen polarization as high as 2〈 ${\mathit{J}}_{\mathit{z}}$ ${\mathrm{〉}}_{\mathrm{H}}$ =0.72(6) has been observed, which is the highest polarization yet produced by this method. However, the rubidium polarization may be limited to this value due to radiation trapping at higher rubidium densities. The spin-relaxation rate of atomic hydrogen on a paraffin-coated cell is also measured and corresponds to about 7600 wall bounces between wall relaxation.We have produced highly spin-polarized atomic hydrogen by spin-exchange optical pumping. A tunable ring dye laser is used to polarize rubidium atoms by optical pumping. The cell containing the rubidium vapor is coated with paraffin in order to reduce spin relaxation due to wall collisions. Hydrogen gas is dissociated in an inductive discharge and flows continuously through the cell, in which the hydrogen atoms are polarized by spin-exchange collisions with the polarized rubidium atoms. Atomic-hydrogen polarization as high as 2〈${\mathit{J}}_{\mathit{z}}$${\mathrm{〉}}_{\mathrm{H}}$=0.72(6) has been observed, which is the highest polarization yet produced by this method. However, the rubidium polarization may be limited to this value due to radiation trapping at higher rubidium densities. The spin-relaxation rate of atomic hydrogen on a paraffin-coated cell is also measured and corresponds to about 7600 wall bounces between wall relaxation.

Physical Review AAug 1, 199035 citations

Hyperfine Relaxation of Optically Pumped Rb87 Atoms in Buffer Gases

Maurice Arditi, T. R. Carver

The hyperfine relaxation of a population difference, produced by optical pumping, between the $F=1$ ${m}_{F}=0$ and $F=2$ ${m}_{F}=0$ energy levels of the ground state of ${\mathrm{Rb}}^{87}$ , has been studied in cells containing neon, argon, helium, or krypton as a buffer gas. The relaxation times ${T}_{1}$ and ${T}_{2}$ have been measured as a function of the rubidium vapor pressure in the cell. The relaxation rate due to spin exchange in ${\mathrm{Rb}}^{87}$ - ${\mathrm{Rb}}^{87}$ collisions has been found equal to 65 ${\mathrm{sec}}^{\ensuremath{-}1}$ at 44\ifmmode^\circ\else\textdegree\fi{}C, and the diffusion coefficients of ${\mathrm{Rb}}^{87}$ atoms in He, Ne, and Ar evaluated as 0.6, 0.31, and 0.22 ${\mathrm{cm}}^{2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$, respectively. The cross section for ${\mathrm{Rb}}^{87}$ -Ne and ${\mathrm{Rb}}^{87}$ -Ar collisions are found to be 1.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$ ${\mathrm{cm}}^{2}$ and 9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$ ${\mathrm{cm}}^{2}$ . These values are in general agreement with values previously obtained by other methods. The extrapolated values of $\frac{1}{{T}_{2}}$ for zero vapor pressure of rubidium are 185, 237, and 318 ${\mathrm{sec}}^{\ensuremath{-}1}$ for Ne, He, or Ar, respectively. Relaxations by the pumping light or by the magnetic field inhomogeneities are also discussed.The hyperfine relaxation of a population difference, produced by optical pumping, between the $F=1$ ${m}_{F}=0$ and $F=2$ ${m}_{F}=0$ energy levels of the ground state of ${\mathrm{Rb}}^{87}$, has been studied in cells containing neon, argon, helium, or krypton as a buffer gas. The relaxation times ${T}_{1}$ and ${T}_{2}$ have been measured as a function of the rubidium vapor pressure in the cell. The relaxation rate due to spin exchange in ${\mathrm{Rb}}^{87}$-${\mathrm{Rb}}^{87}$ collisions has been found equal to 65 ${\mathrm{sec}}^{\ensuremath{-}1}$ at 44\ifmmode^\circ\else\textdegree\fi{}C, and the diffusion coefficients of ${\mathrm{Rb}}^{87}$ atoms in He, Ne, and Ar evaluated as 0.6, 0.31, and 0.22 ${\mathrm{cm}}^{2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$, respectively. The cross section for ${\mathrm{Rb}}^{87}$-Ne and ${\mathrm{Rb}}^{87}$-Ar collisions are found to be 1.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$ ${\mathrm{cm}}^{2}$ and 9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$ ${\mathrm{cm}}^{2}$. These values are in general agreement with values previously obtained by other methods. The extrapolated values of $\frac{1}{{T}_{2}}$ for zero vapor pressure of rubidium are 185, 237, and 318 ${\mathrm{sec}}^{\ensuremath{-}1}$ for Ne, He, or Ar, respectively. Relaxations by the pumping light or by the magnetic field inhomogeneities are also discussed.

Physical ReviewNov 2, 196438 citations

Spin Relaxation of Optically Aligned Rubidium Vapor

W. Franzen

A new optical method for studying the spin relaxation of optically aligned rubidium vapor is described. In this method, the pumping radiation, consisting of circularly polarized ${D}_{1}$ resonance radiation, is suddenly shut off and then turned on again after a known time interval. The relaxation which takes place during the interval of darkness causes the vapor to become more opaque to the pumping radiation at a rate which is determined by the relaxation time. A large degree of alignment, as well as a relaxation time of about 80 milliseconds, were observed in a closed-off evacuated cylindrical glass cell completely lined, except for $\frac{1}{200}$ of the wall area, with a thin film of tetracontane ( ${\mathrm{C}}_{40}$ ${\mathrm{H}}_{82}$ ). The variation of relaxation time with buffer gas pressure was studied in this cell and in an unlined glass cell. From the observations with the unlined cell, diffusion coefficients for rubidium in neon and argon of 0.31 ${\mathrm{cm}}^{2}$ /sec and 0.24 ${\mathrm{cm}}^{2}$ /sec, respectively, can be deduced. Observed cross sections for disorientation collisions between aligned ground-state rubidium atoms and neon, argon, krypton, and xenon atoms are 5.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}23}$ ${\mathrm{cm}}^{2}$ , 3.7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$ ${\mathrm{cm}}^{2}$ , 5.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$ , and 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$ , respectively. In the evacuated tetracontane-lined cell, the relaxation time decreased by 30% for a tenfold increase in rubidium vapor pressure. An explanation for this relatively weak dependence is suggested. The longest observed relaxation time was approximately 0.4 seconds in a tetracontanelined cell filled with neon to a pressure of 3 cm Hg.A new optical method for studying the spin relaxation of optically aligned rubidium vapor is described. In this method, the pumping radiation, consisting of circularly polarized ${D}_{1}$ resonance radiation, is suddenly shut off and then turned on again after a known time interval. The relaxation which takes place during the interval of darkness causes the vapor to become more opaque to the pumping radiation at a rate which is determined by the relaxation time. A large degree of alignment, as well as a relaxation time of about 80 milliseconds, were observed in a closed-off evacuated cylindrical glass cell completely lined, except for $\frac{1}{200}$ of the wall area, with a thin film of tetracontane (${\mathrm{C}}_{40}$${\mathrm{H}}_{82}$). The variation of relaxation time with buffer gas pressure was studied in this cell and in an unlined glass cell. From the observations with the unlined cell, diffusion coefficients for rubidium in neon and argon of 0.31 ${\mathrm{cm}}^{2}$/sec and 0.24 ${\mathrm{cm}}^{2}$/sec, respectively, can be deduced. Observed cross sections for disorientation collisions between aligned ground-state rubidium atoms and neon, argon, krypton, and xenon atoms are 5.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}23}$ ${\mathrm{cm}}^{2}$, 3.7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$ ${\mathrm{cm}}^{2}$, 5.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$, and 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$, respectively. In the evacuated tetracontane-lined cell, the relaxation time decreased by 30% for a tenfold increase in rubidium vapor pressure. An explanation for this relatively weak dependence is suggested. The longest observed relaxation time was approximately 0.4 seconds in a tetracontanelined cell filled with neon to a pressure of 3 cm Hg.

Physical ReviewAug 15, 1959279 citations

{\mathit{J}}_{\mathit{z}}

{\mathrm{〉}}_{\mathrm{H}}

=0.72(6) has been observed, which is the highest polarization yet produced by this method. However, the rubidium polarization may be limited to this value due to radiation trapping at higher rubidium densities. The spin-relaxation rate of atomic hydrogen on a paraffin-coated cell is also measured and corresponds to about 7600 wall bounces between wall relaxation.

The hyperfine relaxation of a population difference, produced by optical pumping, between the

F=1

{m}_{F}=0

and

F=2

{m}_{F}=0

energy levels of the ground state of

{\mathrm{Rb}}^{87}

, has been studied in cells containing neon, argon, helium, or krypton as a buffer gas. The relaxation times

{T}_{1}

and

{T}_{2}

have been measured as a function of the rubidium vapor pressure in the cell. The relaxation rate due to spin exchange in

{\mathrm{Rb}}^{87}

{\mathrm{Rb}}^{87}

collisions has been found equal to 65 ${\mathrm{sec}}^{\ensuremath{-}1}$ at 44\ifmmode^\circ\else\textdegree\fi{}C, and the diffusion coefficients of

{\mathrm{Rb}}^{87}

atoms in He, Ne, and Ar evaluated as 0.6, 0.31, and 0.22

{\mathrm{cm}}^{2}

${\mathrm{sec}}^{\ensuremath{-}1}$, respectively. The cross section for

{\mathrm{Rb}}^{87}

-Ne and

{\mathrm{Rb}}^{87}

-Ar collisions are found to be 1.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$

{\mathrm{cm}}^{2}

and 9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$

{\mathrm{cm}}^{2}

. These values are in general agreement with values previously obtained by other methods. The extrapolated values of

\frac{1}{{T}_{2}}

for zero vapor pressure of rubidium are 185, 237, and 318 ${\mathrm{sec}}^{\ensuremath{-}1}$ for Ne, He, or Ar, respectively. Relaxations by the pumping light or by the magnetic field inhomogeneities are also discussed.

A new optical method for studying the spin relaxation of optically aligned rubidium vapor is described. In this method, the pumping radiation, consisting of circularly polarized

{D}_{1}

resonance radiation, is suddenly shut off and then turned on again after a known time interval. The relaxation which takes place during the interval of darkness causes the vapor to become more opaque to the pumping radiation at a rate which is determined by the relaxation time. A large degree of alignment, as well as a relaxation time of about 80 milliseconds, were observed in a closed-off evacuated cylindrical glass cell completely lined, except for

\frac{1}{200}

of the wall area, with a thin film of tetracontane (

{\mathrm{C}}_{40}

{\mathrm{H}}_{82}

). The variation of relaxation time with buffer gas pressure was studied in this cell and in an unlined glass cell. From the observations with the unlined cell, diffusion coefficients for rubidium in neon and argon of 0.31

{\mathrm{cm}}^{2}

/sec and 0.24

{\mathrm{cm}}^{2}

/sec, respectively, can be deduced. Observed cross sections for disorientation collisions between aligned ground-state rubidium atoms and neon, argon, krypton, and xenon atoms are 5.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}23}$

{\mathrm{cm}}^{2}

, 3.7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$

{\mathrm{cm}}^{2}

, 5.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$

{\mathrm{cm}}^{2}

, and 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}20}$

{\mathrm{cm}}^{2}

, respectively. In the evacuated tetracontane-lined cell, the relaxation time decreased by 30% for a tenfold increase in rubidium vapor pressure. An explanation for this relatively weak dependence is suggested. The longest observed relaxation time was approximately 0.4 seconds in a tetracontanelined cell filled with neon to a pressure of 3 cm Hg.