OPTICAL-DETECTION OF SPIN MULTIPOLE ORDER IN THE GROUND-STATE OF ALKALI ATOMS

Using low light intensities, only spin multipole order of rank k = 1 a nd 2 (orientation and alignment) can be created directly by optical pu mping with sigma(+) and pi polarized light. In order to create and obs erve higher rank multipole order (k > 2) under weak pumping conditions , however, optical pumping and radio-frequency multiple pulse techniqu es can be applied. We observed all allowed ranks of multipole order fo r a given spin system in the single-quantum Zeeman spectra of ground s tate alkali atoms by resorting to the technique of multiple pulse radi o frequency-optical double resonance. The theoretical approach to mode l the experimental results is based on irreducible tensor operators de scribing both the atomic states and the light fields involved, and res ults are in good agreement with the experimental observations for Rb a nd Cs atoms.