Theoretical analysis of D 1 lines of most stable alkali atoms in velocity selective optical pumping (VSOP) spectroscopy is presented by using the approximation of a single cycle of optical pumping in a four-level system. VSOP spectroscopy is clearly compared with polarization spectroscopy and then it is shown that the results obtained for polarization spectroscopy can be applied to the theory in VSOP spectroscopy. The relative signal intensities of Na D 1 line in polarization spectroscopy have been theoretically calculated and experimentally confirmed to be in good agreement with those in VSOP spectroscopy. The first-order theory in VSOP spectroscopy can be applied to the cases of the D 1 lines of the other alkali atoms. It is expected that the theoretical analysis can be useful for future experiments of the Doppler-free D lines in the alkali atoms.
ABS>A detailed physical interpretation of the results of the Barrat- Cohen-Tannoudji theory of the optical pumping cycle is presented. The experimental verification of the essentially new effects that the calculation of the pumping cycle predicts is described. The odd isotopes of mercury were chosen for the experimental verification. The two most important effects predicted by the theory and verified by the experimental work are the radiative effects associated with the absorption process and the partial conservation of coherence'' during the optical pumping cycle. (J.S.R.)