Physical Review A

Light-induced drift of barium atoms

Č. Hradečný, J. Slovák, T. Těthal, I. M. Yermolaev, Evgeniy V. Podivilov

Published Apr 1, 1995• 4 citations

Abstract

An observation of light-induced drift (LID) of atoms with an intermediate metastable level between the ground and excited resonance levels is reported. The drift of atoms of barium was investigated. Molecular nitrogen was used as a buffer gas. The 5d $^{1}$D metastable state of Ba atoms was quenched in collisions with ${\mathrm{N}}_{2}$ molecules. It has been deduced from the experimental results that the collision cross section of Ba atoms with ${\mathrm{N}}_{2}$ molecules is larger for Ba atoms in the ground state than in the 6p $^{1}$P excited state. The maximal LID velocity was about 250 cm/s.

DOI: 10.1103/physreva.51.3374

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Effect of Light-Induced Drift in Confined Semiconductors Heterostructures,

Mark I. Stockman, Lakshmi N. Pandey, Thomas F. George

May 22, 19920 citations

Energy pooling in barium with state excitation

G. De Filippo, Sb R, Slobodan Milošević +1 more

Journal of Physics B Atomic Molecular and Optical PhysicsMay 28, 19968 citations

Quenching of electronically excited barium atoms, Ba(5d 3D J)

Peter G. Whitkop, J. R. Wiesenfeld

The Journal of Chemical PhysicsJan 15, 198022 citations

Coherent population trapping in light-induced drift

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May 21, 19900 citations

Numerical study of light-induced drift of Na in noble gases

Jos E. M. Haverkort, H. G. C. Werij, J. P. Woerdman

Physical Review AOct 1, 198825 citations

Quantum jumps and the single trapped barium ion: Determination of collisional quenching rates for the 5 d2 D5/2 level

Alan A. Madej, J. D. Sankey

Physical Review AMar 1, 199075 citations

Physical Review A

Light-induced drift of barium atoms

Č. Hradečný, J. Slovák, T. Těthal, I. M. Yermolaev, Evgeniy V. Podivilov

Published Apr 1, 1995• 4 citations

Publisher

Abstract

^{1}

D metastable state of Ba atoms was quenched in collisions with

{\mathrm{N}}_{2}

molecules. It has been deduced from the experimental results that the collision cross section of Ba atoms with

{\mathrm{N}}_{2}

molecules is larger for Ba atoms in the ground state than in the 6p

^{1}

P excited state. The maximal LID velocity was about 250 cm/s.

DOI: 10.1103/physreva.51.3374

Related papers

Effect of Light-Induced Drift in Confined Semiconductors Heterostructures,

Mark I. Stockman, Lakshmi N. Pandey, Thomas F. George

Abstract : The effect of light-induced drift (LID) in gases, predicted by Gel'mukhanov and Shalagin and observed later, is manifested in mechanical drift of the absorbing atoms (molecules) in response to optical excitation. The effect of LID takes place if the atom interaction with light is velocity-dependent (due to the Doppler effect), the spectrum of the exciting radiation is asymmetric with respect to the the absorption line, and the absorbing molecules experience collisions with a buffer gas, with the collision rate dependent upon their internal state. The idea of LID is the following. Suppose for the sake of definiteness that the collision frequency of the absorbing molecules with the buffer is greater in the excited state and that the exciting light is red-shifted with respect to the absorption contour. Then due to the Doppler shift, the radiation interacts mainly with the counter-moving molecules, which undergo transitions into an excited state, in which their friction upon the buffer component is increased. Due to this increase, the counter-flying molecules are slowed down, while the molecules moving in the direction of light are not affected. The net effect is a drift of the absorbing component in the direction of light. The drift alternates its direction with the change of signs of either the detaining or the difference in the collision frequencies.Abstract : The effect of light-induced drift (LID) in gases, predicted by Gel'mukhanov and Shalagin and observed later, is manifested in mechanical drift of the absorbing atoms (molecules) in response to optical excitation. The effect of LID takes place if the atom interaction with light is velocity-dependent (due to the Doppler effect), the spectrum of the exciting radiation is asymmetric with respect to the the absorption line, and the absorbing molecules experience collisions with a buffer gas, with the collision rate dependent upon their internal state. The idea of LID is the following. Suppose for the sake of definiteness that the collision frequency of the absorbing molecules with the buffer is greater in the excited state and that the exciting light is red-shifted with respect to the absorption contour. Then due to the Doppler shift, the radiation interacts mainly with the counter-moving molecules, which undergo transitions into an excited state, in which their friction upon the buffer component is increased. Due to this increase, the counter-flying molecules are slowed down, while the molecules moving in the direction of light are not affected. The net effect is a drift of the absorbing component in the direction of light. The drift alternates its direction with the change of signs of either the detaining or the difference in the collision frequencies.

May 22, 19920 citations

Energy pooling in barium with state excitation

G. De Filippo, Sb R, Slobodan Milošević +1 more

Energy-pooling collisions between low-lying excited states of Ba have been studied. We have used a CW dye laser to excite the level in Ba. Radiative decay and collisions with Ba or buffer-gas atoms (Ar, He) populate also the , and metastable levels. The spatial density distributions of these excited levels were measured by the absorption of lines from a Ba hollow-cathode lamp as a function of laser frequency. When the laser was on the exact atomic resonance we observed fluorescence from the , , , , , , and states populated by energy-pooling collisions of Ba( , ). By changing the buffer gas pressure the fluorescence intensity ratio between - and - transitions changes dramatically. This is found to be due to redistribution of population among metastable levels, both in magnitude and space. In addition, we have found that the and metastable levels are also populated when the laser is tuned to the blue from the 553.5 nm line under which conditions a pronounced red-shifted light cone (cone emission) is observed.Energy-pooling collisions between low-lying excited states of Ba have been studied. We have used a CW dye laser to excite the level in Ba. Radiative decay and collisions with Ba or buffer-gas atoms (Ar, He) populate also the , and metastable levels. The spatial density distributions of these excited levels were measured by the absorption of lines from a Ba hollow-cathode lamp as a function of laser frequency. When the laser was on the exact atomic resonance we observed fluorescence from the , , , , , , and states populated by energy-pooling collisions of Ba( , ). By changing the buffer gas pressure the fluorescence intensity ratio between - and - transitions changes dramatically. This is found to be due to redistribution of population among metastable levels, both in magnitude and space. In addition, we have found that the and metastable levels are also populated when the laser is tuned to the blue from the 553.5 nm line under which conditions a pronounced red-shifted light cone (cone emission) is observed.

Journal of Physics B Atomic Molecular and Optical PhysicsMay 28, 19968 citations

Quenching of electronically excited barium atoms, Ba(5d 3D J)

Peter G. Whitkop, J. R. Wiesenfeld

The lowest optically metastable excited state of barium, Ba(5d 3DJ), was populated by laser excitation of the 6p 1P01←6s 1S0 (λ=553.5 nm) transition followed by the spontaneous emission 6p 1P01→5d 3DJ (λ∼1130 nm). No evidence for the normally spin allowed transition 6p 1P01 →5d 1D2 (λ=1500 nm) was obtained. The deactivation of Ba (5d3DJ) by Ba (6s 1S0) is extremely efficient proceeding with a thermal cross section of 1.3±0.1 nm2 at ?730 K. This is in sensible accord with recent calculations of Ba2 potential curves.The lowest optically metastable excited state of barium, Ba(5d 3DJ), was populated by laser excitation of the 6p 1P01←6s 1S0 (λ=553.5 nm) transition followed by the spontaneous emission 6p 1P01→5d 3DJ (λ∼1130 nm). No evidence for the normally spin allowed transition 6p 1P01 →5d 1D2 (λ=1500 nm) was obtained. The deactivation of Ba (5d3DJ) by Ba (6s 1S0) is extremely efficient proceeding with a thermal cross section of 1.3±0.1 nm2 at ?730 K. This is in sensible accord with recent calculations of Ba2 potential curves.

The Journal of Chemical PhysicsJan 15, 198022 citations

Coherent population trapping in light-induced drift

E. R. Eliel, Marc C. de Lignie

Light-induced drift (LID) is a transport phenomenon in a gas mixture with dramatic manifestations such as the optical piston1 and applications in atomic isotope separation.2 The induced drift velocity is proportional to the excited state fraction, and for Na in Xe high drift velocities have been achieved using two lasers.3 Here one laser excites atoms from one hyperfine ground state and the second laser atoms from the other, avoiding hyperfine pumping. Excited in this way, the Na atom represents a Λ type three-level system, where coherent effects can be important.Light-induced drift (LID) is a transport phenomenon in a gas mixture with dramatic manifestations such as the optical piston1 and applications in atomic isotope separation.2 The induced drift velocity is proportional to the excited state fraction, and for Na in Xe high drift velocities have been achieved using two lasers.3 Here one laser excites atoms from one hyperfine ground state and the second laser atoms from the other, avoiding hyperfine pumping. Excited in this way, the Na atom represents a Λ type three-level system, where coherent effects can be important.

May 21, 19900 citations

Numerical study of light-induced drift of Na in noble gases

Jos E. M. Haverkort, H. G. C. Werij, J. P. Woerdman

We present a model for light-induced drift (LID) in the Na--noble-gas system which should enable direct comparison with experiment. In contrast to previous theories of LID based on a two-level description of the optical absorbers and on a simplified collision treatment, the present model is based on a realistic description of laser-driven Na atoms immersed in a buffer gas. Starting from the generalized Bloch equations, we introduce a rate-equation model for the velocity distributions in the four important Na levels. The velocity-changing and fine-structure-changing collisions are described using composite Keilson-Storer collision kernels in which all adjustable parameters have been eliminated by using available literature data. We apply the model in numerical calculations of LID as a function of all experimentally accessible parameters. It is found that the ground-state hyperfine splitting can have large effects on LID, whereas the excited-state fine-structure splitting has not. The paper establishes criteria for optimum LID effects; when using a single-frequency laser the maximum attainable drift velocity is predicted to be 13.8 m/s. Using a proper set of boundary conditions, we find a pressure dependence of LID qualitatively different from the predictions based on previous work. Finally, the influence of the collision model is investigated. We find that LID is independent of the shape of the collision kernel, indicating that a strong-collision model is always valid.We present a model for light-induced drift (LID) in the Na--noble-gas system which should enable direct comparison with experiment. In contrast to previous theories of LID based on a two-level description of the optical absorbers and on a simplified collision treatment, the present model is based on a realistic description of laser-driven Na atoms immersed in a buffer gas. Starting from the generalized Bloch equations, we introduce a rate-equation model for the velocity distributions in the four important Na levels. The velocity-changing and fine-structure-changing collisions are described using composite Keilson-Storer collision kernels in which all adjustable parameters have been eliminated by using available literature data. We apply the model in numerical calculations of LID as a function of all experimentally accessible parameters. It is found that the ground-state hyperfine splitting can have large effects on LID, whereas the excited-state fine-structure splitting has not. The paper establishes criteria for optimum LID effects; when using a single-frequency laser the maximum attainable drift velocity is predicted to be 13.8 m/s. Using a proper set of boundary conditions, we find a pressure dependence of LID qualitatively different from the predictions based on previous work. Finally, the influence of the collision model is investigated. We find that LID is independent of the shape of the collision kernel, indicating that a strong-collision model is always valid.

Physical Review AOct 1, 198825 citations

Quantum jumps and the single trapped barium ion: Determination of collisional quenching rates for the 5 d2 D5/2 level

Alan A. Madej, J. D. Sankey

A single ${\mathrm{Ba}}^{+}$ atom was confined in a radio-frequency ion trap and cooled by near-resonant laser light. Quantum jumps into and out of the metastable 5d $^{2}D_{5/2}$ level were observed that followed the expected exponential distribution in dark periods to good agreement. Measurement of quantum-jump distributions together with careful measurements of the absolute partial pressures of all residual gas species enabled accurate measurements of the quenched 5d $^{2}D_{5/2}$ lifetime as a function of quenching gas pressure. Measurements of quenching were observed at pressures where the mean collision rate was on the order of 1 ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The results yielded quenching rate constants for the metastable level for a series of gases that typically make up the residual gas environment of ultra-high-vacuum systems ( ${\mathrm{H}}_{2}$ , He, ${\mathrm{CH}}_{4}$ , ${\mathrm{H}}_{2}$ O, CO, ${\mathrm{N}}_{2}$ , Ar, and ${\mathrm{CO}}_{2}$ ) together with an improved value of the ${5}^{2}$ ${\mathrm{D}}_{5/2}$ radiative lifetime of ${t}_{0}$ =34.5\ifmmode\pm\else\textpm\fi{}3.5 s. The above quenching rate constants were then compared with classical ion-molecule collision theory. It was found that the quenching rates for molecular gases were comparable to the classical collision rates, while the rates for atomic gases were considerably lower.A single ${\mathrm{Ba}}^{+}$ atom was confined in a radio-frequency ion trap and cooled by near-resonant laser light. Quantum jumps into and out of the metastable 5d $^{2}D_{5/2}$ level were observed that followed the expected exponential distribution in dark periods to good agreement. Measurement of quantum-jump distributions together with careful measurements of the absolute partial pressures of all residual gas species enabled accurate measurements of the quenched 5d $^{2}D_{5/2}$ lifetime as a function of quenching gas pressure. Measurements of quenching were observed at pressures where the mean collision rate was on the order of 1 ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The results yielded quenching rate constants for the metastable level for a series of gases that typically make up the residual gas environment of ultra-high-vacuum systems (${\mathrm{H}}_{2}$, He, ${\mathrm{CH}}_{4}$, ${\mathrm{H}}_{2}$O, CO, ${\mathrm{N}}_{2}$, Ar, and ${\mathrm{CO}}_{2}$) together with an improved value of the ${5}^{2}$${\mathrm{D}}_{5/2}$ radiative lifetime of ${t}_{0}$=34.5\ifmmode\pm\else\textpm\fi{}3.5 s. The above quenching rate constants were then compared with classical ion-molecule collision theory. It was found that the quenching rates for molecular gases were comparable to the classical collision rates, while the rates for atomic gases were considerably lower.

Physical Review AMar 1, 199075 citations

^{1}

D metastable state of Ba atoms was quenched in collisions with

{\mathrm{N}}_{2}

molecules. It has been deduced from the experimental results that the collision cross section of Ba atoms with

{\mathrm{N}}_{2}

molecules is larger for Ba atoms in the ground state than in the 6p

^{1}

P excited state. The maximal LID velocity was about 250 cm/s.

A single

{\mathrm{Ba}}^{+}

atom was confined in a radio-frequency ion trap and cooled by near-resonant laser light. Quantum jumps into and out of the metastable 5d

^{2}D_{5/2}

level were observed that followed the expected exponential distribution in dark periods to good agreement. Measurement of quantum-jump distributions together with careful measurements of the absolute partial pressures of all residual gas species enabled accurate measurements of the quenched 5d

^{2}D_{5/2}

lifetime as a function of quenching gas pressure. Measurements of quenching were observed at pressures where the mean collision rate was on the order of 1 ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The results yielded quenching rate constants for the metastable level for a series of gases that typically make up the residual gas environment of ultra-high-vacuum systems (

{\mathrm{H}}_{2}

, He,

{\mathrm{CH}}_{4}

{\mathrm{H}}_{2}

O, CO,

{\mathrm{N}}_{2}

, Ar, and

{\mathrm{CO}}_{2}

) together with an improved value of the

{5}^{2}

{\mathrm{D}}_{5/2}

radiative lifetime of

{t}_{0}

=34.5\ifmmode\pm\else\textpm\fi{}3.5 s. The above quenching rate constants were then compared with classical ion-molecule collision theory. It was found that the quenching rates for molecular gases were comparable to the classical collision rates, while the rates for atomic gases were considerably lower.