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In this thesis, I describe the spectroscopic investigations and preliminary results of evaporative cooling of rubidium atoms done on a magnetic trap dressed with a radiofrequency field. Unlike the case of a static magnetic trap, where a single radiofrequency photon is used to outcouple atoms we have demonstrated that a multiphoton transition is necessary. This transitions are nearly resonant with the energy spacing of the radiofrequency dressed states. The evaporation efficiency is not the same for all the observed transitions: the transition involving a two photon process is more efficient compared to the others. Preliminary results of evaporative cooling in a radiofrequency dressed trap are discussed. The quantum degeneracy is not reached as it is difficult to reach thermalization due to the strong anisotropy in the trap. A way to render the evaporative cooling more efficient is to increase the horizontal oscillation frequencies. Finally, we discuss a method to load the atoms into a radiofrequency dressed quadrupole trap, leading to large oscillation frequencies in the horizontal directions.
key words: Bose-Einstein condensation – 2D gas – rubidium – dressed atoms – radiofrequency field – adiabatic potentials – spectroscopy – evaporative cooling