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Coherent population trapping in light-induced drift

E. R. Eliel, Marc C. de Lignie

Published May 21, 1990• 0 citations
OpenAlex

Abstract

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.

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Light-induced drift with low-power spectrally shaped lasers: efficient isotope separation and high drift velocities

E. R. Eliel, Alan D. Streater, J. P. Woerdman

The use of paraffin-coated cells has led to a breakthrough in the experimental study of light-induced drift (LID) of alkalis in noble gases. In recent experiments isotope separation of the two naturally occurring Rb isotopes through the LID effect has been achieved (enrichment of the rare isotope up to 95%), 1,2 and direct measurements of the drift velocity of Na in noble gases as a function of various experimental parameters have been made.3 In these experiments a single single-mode dye laser, tuned within the Doppler profile of the resonance line, was used to excite a specific velocity group of atoms (isotope selective in the case of Rb). Optical pumping between the ground-state hyperfine levels F = I+½ and F=I−½ plays a dominant (limiting) role in determining the magnitude of the LID effects by strongly depleting the resonantly excited hyperfine substate (of a specific isotope).

Conference on Lasers and Electro-Optics•Apr 25, 1988•0 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.

Physical Review A•Oct 1, 1988•25 citations

The optical piston: a new mechanical action of light

J. P. Woerdman, Jos E. M. Haverkort, H. G. C. Werij +1 more

Light-induced drift (LID) occurs in a binary gas mixture when one constituent of the mixture is velocity selectively excited and when the mobility of that constituent is state dependent.1 In the case of large optical thickness, LID manifests itself in a spectacular way as an optical piston.2,3 We report here on a new regime of this optical piston and on a realistic multilevel description of LID in alkali-noble gas mixtures.

•Jun 9, 1986•0 citations

Study of the optical piston

H. G. C. Werij, Jos E. M. Haverkort, Paul C. M. Planken +5 more

In the past, interpretation of light-induced drift (LID) effects in alkali–noble gas mixtures in capillary cells has been severely complicated by surface interactions. As an example, the velocity of the optical piston, a spectacular manifestation of LID, is limited by adsorption–desorption processes to a value in the mm/s range.1 Recently, a breakthrough has been made: by coating the capillary wall with paraffin the surface interaction has been completely eliminated leading to transport velocities in the m/s range and allowing a study of LID in its pure form.2 Here we report the first measurements of the detuning and intensity dependence of the drift velocity in Na–noble gas mixtures and compare these to theory.

Journal of the Optical Society of America B•Feb 1, 1987•0 citations

Study of the optical piston

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

We report an experimental and theoretical study of the optical piston, a consequence of the phenomenon of light-induced drift (LID), observed in binary mixtures of Na vapor and a buffer gas. Good agreement has been found between experiment and existing theory as far as the shape of the Na density profile in the piston is concerned. The piston velocity is anomalously low; this is accounted for by incorporating the effects of adsorption and desorption into the theory. Furthermore, we introduce a rate-equation model for LID which incorporates the fine and hyperfine structure of the level scheme of the Na absorbers; this gives insight into the sublevel velocity distributions and the nonequilibrium part of the total velocity distribution during LID.

Physical Review A•May 1, 1986•63 citations

Light-induced drift velocities in Na–noble-gas mixtures

H. G. C. Werij, Jos E. M. Haverkort, Paul C. M. Planken +5 more

We report direct quantitative measurements of the light-induced drift velocity in Na--noble-gas mixtures under well-defined conditions. Results are in excellent agreement with predictions from a realistic numerical model incorporating the multilevel structure of the Na atom. The effect of optical hyperfine pumping on light-induced drift is investigated. Limiting values for the drift velocity are predicted.

Physical Review Letters•Jun 22, 1987•49 citations
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.
The use of paraffin-coated cells has led to a breakthrough in the experimental study of light-induced drift (LID) of alkalis in noble gases. In recent experiments isotope separation of the two naturally occurring Rb isotopes through the LID effect has been achieved (enrichment of the rare isotope up to 95%), 1,2 and direct measurements of the drift velocity of Na in noble gases as a function of various experimental parameters have been made.3 In these experiments a single single-mode dye laser, tuned within the Doppler profile of the resonance line, was used to excite a specific velocity group of atoms (isotope selective in the case of Rb). Optical pumping between the ground-state hyperfine levels F = I+½ and F=I−½ plays a dominant (limiting) role in determining the magnitude of the LID effects by strongly depleting the resonantly excited hyperfine substate (of a specific isotope).
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.
In the past, interpretation of light-induced drift (LID) effects in alkali–noble gas mixtures in capillary cells has been severely complicated by surface interactions. As an example, the velocity of the optical piston, a spectacular manifestation of LID, is limited by adsorption–desorption processes to a value in the mm/s range.1 Recently, a breakthrough has been made: by coating the capillary wall with paraffin the surface interaction has been completely eliminated leading to transport velocities in the m/s range and allowing a study of LID in its pure form.2 Here we report the first measurements of the detuning and intensity dependence of the drift velocity in Na–noble gas mixtures and compare these to theory.
We report an experimental and theoretical study of the optical piston, a consequence of the phenomenon of light-induced drift (LID), observed in binary mixtures of Na vapor and a buffer gas. Good agreement has been found between experiment and existing theory as far as the shape of the Na density profile in the piston is concerned. The piston velocity is anomalously low; this is accounted for by incorporating the effects of adsorption and desorption into the theory. Furthermore, we introduce a rate-equation model for LID which incorporates the fine and hyperfine structure of the level scheme of the Na absorbers; this gives insight into the sublevel velocity distributions and the nonequilibrium part of the total velocity distribution during LID.