Journal of Physics B Atomic Molecular and Optical Physics
Interference effects in the two-photon polarization spectra of alkali atoms in intermediate strength magnetic fields
P. C. Stancil, G. E. Copeland
Abstract
The degree of linear polarization P L for two-photon absorption of alkali atoms in intermediate strength magnetic fields has been computationally investigated. Polarization spectra were obtained for n a s 2 S 1/2 to n b s 2 S 1/2 transitions with the photons in near resonance with intermediate 2 P j levels. Previous experiments and calculations in the absence of a magnetic held revealed a complete polarization reversal (P L approximately -100%) for frequencies near resonance between the 2 P 1/2 and 2 P 3/2 levels due to fine-structure coherence. Application of weak to intermediate strength fields induce additional depolarization features as a result of anomalous Zeeman splitting. The fine-structure depolarization feature disappears for strong fields (Paschen-Back regime), while the calculations predict that Zeeman depolarization persists though the transitions become forbidden. Magnetic-field-dependent polarization spectra can be measured in the laboratory with high precision and it should prove interesting to trace through the weak, intermediate, and strong field regimes.