Highly Excited States of Ultracold Molecules: Photoassociative Spectroscopy ofNa2

Abstract

We describe the spectroscopy of highly excited states of ultracold ${\mathrm{Na}}_{2}$ molecules using a new photoassociative approach based on resonantly enhanced multiphoton ionization. We excite a remarkable number of ${\mathrm{Na}}_{2}$ rotational states providing a rich rovibrational spectrum. We thereby extract not only the first order quadrupole-quadrupole ( ${C}_{5}$) and the van der Waals constants ( ${C}_{6}$) but also sensitive atom-atom interaction parameters such as spin-spin, spin-orbit, and perturbative constants.