  We have recently demonstrated that optical pumping methods combined with
photoassociation of ultra-cold atoms can produce ultra-cold and dense samples
of molecules in their absolute rovibronic ground state. More generally, both
the external and internal degrees of freedom can be cooled by addressing
selected rovibrational levels on demand. Here, we recall the basic concepts and
main steps of our experiments, including the excitation schemes and detection
techniques we use to achieve the rovibrational cooling of Cs2 molecules. In
addition, we present the determination of formation pathways and a theoretical
analysis explaining the experimental observations. These simulations improves
the spectroscopic knowledge required to transfer molecules to any desired
rovibrational level.
