Light-shift tomography in an optical-dipole trap for neutral atoms

We report on light-shift tomography of a cloud of ⁸⁷Rb atoms in a far-detuned optical-dipole trap at 15650.3em0exnm. Our method is based on standard absorption imaging, but takes advantage of the strong light shift of the excited state of the imaging transition, which is due to a quasiresonance of the trapping laser with a higher excited level. We use this method to (i) map the equipotentials of a crossed optical-dipole trap and (ii) study the thermalization of an atomic cloud by following the evolution of the potential energy of atoms during the free-evaporation process.