Mj selectivity in collisional energy transfer between alkali-metal atoms

Abstract

Na atoms in the magnetic field have been selectively excited to each Zeeman sub-level of either the 3p²P_1/2 or 3p ²P_3/2 state by a tunable dye laser and the Zeeman spectra of the fluorescence from the collisional populated 3p ²P levels have been measured. From the intensities of the Zeeman lines, the selectivity in the collisional transitions between the Zeeman sub-levels of the 3p ²P_1/2 and 3p ²P_3/2 states has been directly specified. The time evolution of the σ-polarized fluorescence intensity of the Na(3p ²P_1/2→ 3s ²S_1/2) transition has been measured following the Na(3p ²P_3/2â†� 3s ²S_1/2) excitation by a σ-polarized short light pulse at H= 129 G. An amplitude modulation was found in the fluorescence from the collisional energy transferred state Na(3p ²P_1/2). This is the first observation of quantum beats in collision-induced fluorescence. The frequency of the modulation coincides very well with that of the quantum beats of the resonance fluorescence Na(3p ²P_3/2→ 3s ²S_1/2), but the phases are opposite. These results are explained by assuming the conservation of coherence during collisional energy transfer.