Comparison of multilevel atomic schemes for SubDoppler laser cooling

We present the results of the kinetic theory of laser cooling for four basi c multilevel atomic schemes: (3+5)-, (5+7)-, (7+9)-, and (9+11)-level atoms in a sigma (+) - sigma (-) field configuration. The underlying physical pr ocesses and the effectiveness of laser cooling are compared for the differe nt models. We show that even-order multiphoton processes caused by two lase r waves can be identified as the basic physical mechanism responsible for t he subDoppler laser cooling of atoms. The temperature of laser-cooled atoms is derived for all four models and is found to be lower for atomic schemes with bigger numbers of sublevels.