Optical Pumping and Related Effects

Lucile Julien, M. Pinard

Reports the optogalvanic detection of observables induced by optical pumping in metastable states of neon. As with optical methods signals are obtained which are related to electronic and nuclear orientation or alignment. Many optical pumping experiments may thus be performed using optogalvanic techniques, including the Hanle effect and 'velocity selective optical pumping' described. Different mechanisms are discussed from which optogalvanic signals related to non-scalar observables may originate. Profiles obtained from frequency sweeps of two polarisation-modulated counterpropagating pump beams indicate the dominant mechanism is a second-order pumping effect which induces a modulated depletion of the metastable state. No effect has been observed arising from a variation of the Penning collision cross section when the two metastable colliding atoms are oriented. The analogy between signals produced by optogalvanic and optical methods are pointed out.

George William Series

Han Seb Moon, Lim Lee, Jung Bog Kim

We have studied double-resonance optical pumping (DROP) as a function of the polarization combination of lasers, laser power, and the alignment of lasers in the 5S1/2-5P3/2-D3/2,5/2 ladder-type system of Rb87 atoms. By considering the two-photon transition probability and optical pumping effects, the changes in the relative magnitude of the DROP hyperfine structures as a function of the polarization combination of the lasers were analyzed theoretically. The theoretical results are in good agreement with the experimental results. Owing to the low optical pumping effect in the cycling transition, we could see the dependence of the spectrum on the laser power in the 5P3/2-4D5/2 transition distinctly. Also, the spectral linewidths as a function of the alignment between the lasers were measured 12.2 MHz for copropagating beams and 6.9 MHz for counterpropagating beams.

Robert A. Bernheim, Ernst K. Franke

А. Ч. Измайлов

New sub-Doppler resonances at central frequencies of atomic (molecular) transitions that appear in the spectrum of absorption of the probe optical radiation under the influence of optical pumping propagating in the orthogonal direction through a relatively narrow area of a cylindrical cell containing dilute gas medium are discovered and analyzed. These resonances are induced by specific optical pumping of atoms as they fly freely from the inner cell surface through the pumped region toward the probe optical beam. The obtained mathematical relations are used to investigate the dependence of the discussed resonances on the intensity and spatial distribution of the localized optical pumping. The proposed method could allow reducing the Doppler broadening of the detected spectral lines by the factor equal to the ratio of the effective width of the narrow pumped region to the cell radius. The obtained results may find application in high-resolution spectroscopy of atoms (molecules), as well as for laser-frequency stabilization by using the discovered sub- Doppler resonances.