Two-photon photoassociation spectroscopy of heteronuclear YbRb.

We report on the spectroscopic investigation of vibrational levels in the electronic ground state of the heteronuclear molecule (176)Yb(87)Rb. Using two-photon photoassociation spectroscopy in a laser-cooled mixture of (176)Yb and (87)Rb we are able to determine the binding energies of weakly-bound vibrational levels. By applying the LeRoy-Bernstein method we assign the vibrational quantum numbers and deduce a C(6) coefficient for the long-range part of the molecular potential of ∼2500 a.u.