Sisyphus cooling of rubidium atoms on the D-2 (F=1 -> F '=1) line: The role of the neighbouring transitions

We study one-dimensional Sisyphus cooling on the 5S(1/2)(F = 1) --> 5P(3/2) (F' = 1) transition of Rb-87 atoms in the electric field created by two cou nter-propagating linearly polarized laser beams with an angle of theta betw een the polarization directions. The neighbouring F' = 0 and F' = 2 excited states are found to play an important role in the cooling mechanism, e.g., by inhibiting a significant population of the velocity-selective dark stat e. Our experimental data, such as temperatures and probe absorption coeffic ients, agree well with the results of quantum Monte-Carlo wavefunction simu lations.