Optical beam size effects in spin polarized pumping

We have experimentally and theoretically investigate the effect of optical pump beam size on narrowband spin polarized optical pumping of alkali atom vapor. We developed a six-level model describing narrowband spin polarized optical pumping of alkali atoms and applied this model to an atomic vapor cell, accounting for atomic transit time through the optical beam and wall collision effects. Our expression for the wall collision effects is derived from the diffusion model. Overall, we obtained good agreement between theory and experimentally measured relaxation time constants.