Physical Review A

Concentration of atomic population in any single-ground-state magnetic sublevel in alkali-metal vapors

Natarajan D. Bhaskar

Published Jun 1, 1993• 9 citations

Abstract

A scheme for concentrating a large fraction (\ensuremath{\sim}100%) of the alkali-metal atoms in an atomic vapor in any single magnetic sublevel of the ground state is developed. This is experimentally demonstrated in the $^{87}\mathrm{Rb}$ vapor. The atomic vapor is optically pumped to a high degree of spin polarization after which two radio-frequency \ensuremath{\pi} pulses are applied to transfer the atomic population from the (2,2) or (2,-2) (F,${\mathit{M}}_{\mathit{F}}$) state to the (2,0) sublevel of the ground state. The resulting distribution is diagnosed using a microwave field tuned to the hyperfine transition (6834 MHz).

DOI: 10.1103/physreva.47.r4559

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Multistep preparation into a single Zeeman sublevel in a Rb87 vapor cell: Theory and experiment

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Physical ReviewDec 15, 195788 citations

Physical Review A

Concentration of atomic population in any single-ground-state magnetic sublevel in alkali-metal vapors

Natarajan D. Bhaskar

Published Jun 1, 1993• 9 citations

Publisher

Abstract

^{87}\mathrm{Rb}

vapor. The atomic vapor is optically pumped to a high degree of spin polarization after which two radio-frequency \ensuremath{\pi} pulses are applied to transfer the atomic population from the (2,2) or (2,-2) (F,

{\mathit{M}}_{\mathit{F}}

) state to the (2,0) sublevel of the ground state. The resulting distribution is diagnosed using a microwave field tuned to the hyperfine transition (6834 MHz).

DOI: 10.1103/physreva.47.r4559

Related papers

Multistep preparation into a single Zeeman sublevel in a Rb87 vapor cell: Theory and experiment

Salvatore Micalizio, Aldo Godone, Filippo Levi +1 more

In this paper we propose a pumping scheme to concentrate nearly all the atoms of an alkali-metal vapor into one of the ground-state Zeeman sublevels. We report theory and experiment for the case of $^{87}\text{R}\text{b}$ in a cell with buffer gas but the technique easily applies to other alkali-metal atoms. The pumping scheme consists of a suitable sequence of laser and microwave pulses after which a large fraction of atoms is transferred into the desired level. The efficiency of this technique depends mainly on the laser power and on the relaxation effects taking place inside the cell; in principle, more than 95% of the atoms can be prepared in a well-defined quantum state. Diagnostic of the resulting population distribution is made observing the free-induction decay signal at the output of a microwave cavity. This multistep laser-microwave pumping technique is particularly suited for compact vapor-cell frequency standards working in pulsed regime or in experiments where it is necessary to maintain the cylindrical symmetry of the experimental arrangement.In this paper we propose a pumping scheme to concentrate nearly all the atoms of an alkali-metal vapor into one of the ground-state Zeeman sublevels. We report theory and experiment for the case of $^{87}\text{R}\text{b}$ in a cell with buffer gas but the technique easily applies to other alkali-metal atoms. The pumping scheme consists of a suitable sequence of laser and microwave pulses after which a large fraction of atoms is transferred into the desired level. The efficiency of this technique depends mainly on the laser power and on the relaxation effects taking place inside the cell; in principle, more than 95% of the atoms can be prepared in a well-defined quantum state. Diagnostic of the resulting population distribution is made observing the free-induction decay signal at the output of a microwave cavity. This multistep laser-microwave pumping technique is particularly suited for compact vapor-cell frequency standards working in pulsed regime or in experiments where it is necessary to maintain the cylindrical symmetry of the experimental arrangement.

Physical Review AAug 24, 200916 citations

Production of Atomic Alkali-Metal Beams in Single Hyperfine Sublevels

W. Dreves, H.J. Jänsch, Edmund Koch +1 more

A compact source which produces atomic alkali-metal beams in individual hyperfine sublevels has been developed. The methods are demonstrated with $^{23}\mathrm{Na}$ atoms. Initially nearly all atoms are transferred into one hyperfine sublevel ( $|F, {m}_{F}〉=|2, 2〉$ ) by a double-resonance technique using laser optical pumping and rf transitions. Subsequently the other hyperfine sublevels can be populated selectively by an adiabatic high-frequency transition. The hyperfine sublevel populations are determined by laser-induced fluorescence spectroscopy in a magnetic field.A compact source which produces atomic alkali-metal beams in individual hyperfine sublevels has been developed. The methods are demonstrated with $^{23}\mathrm{Na}$ atoms. Initially nearly all atoms are transferred into one hyperfine sublevel ($|F, {m}_{F}〉=|2, 2〉$) by a double-resonance technique using laser optical pumping and rf transitions. Subsequently the other hyperfine sublevels can be populated selectively by an adiabatic high-frequency transition. The hyperfine sublevel populations are determined by laser-induced fluorescence spectroscopy in a magnetic field.

Physical Review LettersMay 30, 198350 citations

Spin Polarization of an Ensemble of Alkali Atoms with Zero Average Magnetization

V. A. Bobrikova, Е. Н. Попов, К. А. Баранцев +2 more

The Landé factors of hyperfine sublevels belonging to the same spectral term differ from each other. This leads to the appearance of an effective gyromagnetic ratio for an atomic ensemble, which can be defined as the ratio of the average magnetic moment to the average angular momentum. Characteristically, this quantity is not a constant, but rather depends on the populations of the hyperfine sublevels. States of an ensemble of atoms occupying their ground level in which the effective gyromagnetic ratio is zero are of much interest. Here, one of such states is considered by the example of alkali metal 87 Rb. The main idea is to suggest a method for preparing states with zero effective gyromagnetic ratio by means of two-frequency pumping of a saturated alkali-metal vapor in a cell containing a buffer gas. It is noteworthy that, according to calculations, correlation between the two fields is not required for attaining this goal.The Landé factors of hyperfine sublevels belonging to the same spectral term differ from each other. This leads to the appearance of an effective gyromagnetic ratio for an atomic ensemble, which can be defined as the ratio of the average magnetic moment to the average angular momentum. Characteristically, this quantity is not a constant, but rather depends on the populations of the hyperfine sublevels. States of an ensemble of atoms occupying their ground level in which the effective gyromagnetic ratio is zero are of much interest. Here, one of such states is considered by the example of alkali metal 87 Rb. The main idea is to suggest a method for preparing states with zero effective gyromagnetic ratio by means of two-frequency pumping of a saturated alkali-metal vapor in a cell containing a buffer gas. It is noteworthy that, according to calculations, correlation between the two fields is not required for attaining this goal.

Journal of Experimental and Theoretical Physics LettersJun 1, 20181 citation

Optical Methods of Atomic Orientation and of Magnetic Resonance*

Alfred Kastler

In the optical excitation of atoms with polarized light, producing excited atoms, only some of the Zeeman sublevels of the excited state are actually reached, so that large differences of population can be built up between Zeeman sublevels or between hyperfine structure (hfs) levels. This property can be used to detect radio-frequency resonance in optically excited atomic states. These resonances produce a characteristic change in intensity or in the degree of polarization of the light re-emitted. Zeeman intervals, Stark effects, and hfs intervals can be measured in this manner. (The Stark constant of the 63P1 level of Hg and the electric quadrupole moments of the alkali atoms have been obtained in this way.)The technique of “optical pumping” gives a way to concentrate atoms in some of the Zeeman sublevels of one of the hfs levels of the ground state.Atomic orientation has been obtained with the Na atom, in an atomic beam and in the vapor in equilibrium with the metal. The orientation effects have been studied by detection of radio-frequency resonance signals in the ground state. Orientation can be increased many times by adding a variable pressure of a foreign gas to the pure Na vapor. Because of the coupling between nuclear spin and electron spin, nuclear orientation is produced at the same time as atomic orientation.In the optical excitation of atoms with polarized light, producing excited atoms, only some of the Zeeman sublevels of the excited state are actually reached, so that large differences of population can be built up between Zeeman sublevels or between hyperfine structure (hfs) levels. This property can be used to detect radio-frequency resonance in optically excited atomic states. These resonances produce a characteristic change in intensity or in the degree of polarization of the light re-emitted. Zeeman intervals, Stark effects, and hfs intervals can be measured in this manner. (The Stark constant of the 63P1 level of Hg and the electric quadrupole moments of the alkali atoms have been obtained in this way.)The technique of “optical pumping” gives a way to concentrate atoms in some of the Zeeman sublevels of one of the hfs levels of the ground state.Atomic orientation has been obtained with the Na atom, in an atomic beam and in the vapor in equilibrium with the metal. The orientation effects have been studied by detection of radio-frequency resonance signals in the ground state. Orientation can be increased many times by adding a variable pressure of a foreign gas to the pure Na vapor. Because of the coupling between nuclear spin and electron spin, nuclear orientation is produced at the same time as atomic orientation.

Journal of the Optical Society of AmericaJun 1, 1957223 citations

Spontaneous spin polarization and bistability in atomic vapors by optical pumping with unpolarized light

Norval Fortson, Blayne R. Heckel

A vapor of paramagnetic atoms, under conditions in which electronic spin exchange takes place faster than collisional spin relaxation, should acquire a spontaneous spin polarization when illuminated by unpolarized light tuned to excite only certain ground-state atomic hyperfine levels. In magnetic fields above a certain size, the atomic polarization has two stable states, either parallel or antiparallel to the field. Experiments to demonstrate this effect and explore possible applications may be feasible by the use of alkali-metal vapors.A vapor of paramagnetic atoms, under conditions in which electronic spin exchange takes place faster than collisional spin relaxation, should acquire a spontaneous spin polarization when illuminated by unpolarized light tuned to excite only certain ground-state atomic hyperfine levels. In magnetic fields above a certain size, the atomic polarization has two stable states, either parallel or antiparallel to the field. Experiments to demonstrate this effect and explore possible applications may be feasible by the use of alkali-metal vapors.

Physical Review LettersSep 21, 198721 citations

Atomic Orientation by Optical Pumping

W. Franzen, A. G. Emslie

A variation of the usual method of atomic orientation of alkali metal vapors by optical pumping is proposed. This variation consists of employing a single circularly polarized ${D}_{1}$ line as pumping radiation, instead of a mixture of the two $D$ lines. Under these conditions, one magnetic substate of the ground state is transparent to the pumping radiation. It is shown that for a sufficiently intense light source and relatively weak relaxation, the entire population of the vapor will tend to be pumped into this single state, resulting in nearly one-hundred percent atomic orientation. The pumping process is analyzed in detail for sodium vapor illuminated with $3{P}_{\frac{1}{2}}\ensuremath{-}3{S}_{\frac{1}{2}}$ radiation, and the time dependence of the populations of the eight magnetic sublevels of the ground state is computed. It is shown that in the steady state, the light absorption by the vapor is linear rather than exponential with distance. A simple method of measuring relaxation times based on this observation is suggested. The conditions under which the imprisonment of resonance radiation limits the size of the oriented sample are discussed, and it is suggested that the proposed technique will allow the alignment of larger samples than is possible by the usual method of optical pumping.A variation of the usual method of atomic orientation of alkali metal vapors by optical pumping is proposed. This variation consists of employing a single circularly polarized ${D}_{1}$ line as pumping radiation, instead of a mixture of the two $D$ lines. Under these conditions, one magnetic substate of the ground state is transparent to the pumping radiation. It is shown that for a sufficiently intense light source and relatively weak relaxation, the entire population of the vapor will tend to be pumped into this single state, resulting in nearly one-hundred percent atomic orientation. The pumping process is analyzed in detail for sodium vapor illuminated with $3{P}_{\frac{1}{2}}\ensuremath{-}3{S}_{\frac{1}{2}}$ radiation, and the time dependence of the populations of the eight magnetic sublevels of the ground state is computed. It is shown that in the steady state, the light absorption by the vapor is linear rather than exponential with distance. A simple method of measuring relaxation times based on this observation is suggested. The conditions under which the imprisonment of resonance radiation limits the size of the oriented sample are discussed, and it is suggested that the proposed technique will allow the alignment of larger samples than is possible by the usual method of optical pumping.

Physical ReviewDec 15, 195788 citations

^{87}\mathrm{Rb}

{\mathit{M}}_{\mathit{F}}

) state to the (2,0) sublevel of the ground state. The resulting distribution is diagnosed using a microwave field tuned to the hyperfine transition (6834 MHz).

In this paper we propose a pumping scheme to concentrate nearly all the atoms of an alkali-metal vapor into one of the ground-state Zeeman sublevels. We report theory and experiment for the case of

^{87}\text{R}\text{b}

in a cell with buffer gas but the technique easily applies to other alkali-metal atoms. The pumping scheme consists of a suitable sequence of laser and microwave pulses after which a large fraction of atoms is transferred into the desired level. The efficiency of this technique depends mainly on the laser power and on the relaxation effects taking place inside the cell; in principle, more than 95% of the atoms can be prepared in a well-defined quantum state. Diagnostic of the resulting population distribution is made observing the free-induction decay signal at the output of a microwave cavity. This multistep laser-microwave pumping technique is particularly suited for compact vapor-cell frequency standards working in pulsed regime or in experiments where it is necessary to maintain the cylindrical symmetry of the experimental arrangement.

A compact source which produces atomic alkali-metal beams in individual hyperfine sublevels has been developed. The methods are demonstrated with

^{23}\mathrm{Na}

atoms. Initially nearly all atoms are transferred into one hyperfine sublevel (

|F, {m}_{F}〉=|2, 2〉

) by a double-resonance technique using laser optical pumping and rf transitions. Subsequently the other hyperfine sublevels can be populated selectively by an adiabatic high-frequency transition. The hyperfine sublevel populations are determined by laser-induced fluorescence spectroscopy in a magnetic field.

A variation of the usual method of atomic orientation of alkali metal vapors by optical pumping is proposed. This variation consists of employing a single circularly polarized

{D}_{1}

line as pumping radiation, instead of a mixture of the two

D

lines. Under these conditions, one magnetic substate of the ground state is transparent to the pumping radiation. It is shown that for a sufficiently intense light source and relatively weak relaxation, the entire population of the vapor will tend to be pumped into this single state, resulting in nearly one-hundred percent atomic orientation. The pumping process is analyzed in detail for sodium vapor illuminated with $3{P}_{\frac{1}{2}}\ensuremath{-}3{S}_{\frac{1}{2}}$ radiation, and the time dependence of the populations of the eight magnetic sublevels of the ground state is computed. It is shown that in the steady state, the light absorption by the vapor is linear rather than exponential with distance. A simple method of measuring relaxation times based on this observation is suggested. The conditions under which the imprisonment of resonance radiation limits the size of the oriented sample are discussed, and it is suggested that the proposed technique will allow the alignment of larger samples than is possible by the usual method of optical pumping.