Photoassociation spectroscopy of a degenerate Fermi gas of 173 Ytterbium atoms

We report photoassociation (PA) spectroscopy of ultracold $^{173}$Yb fermions near dissociation limit with dipole-forbidden intercombination transition. The photoassociative spectrum is measured with red-detuned lasers over a scan range up to 1GHz with respect to the F=5/2 $\rightarrow$ F$^\prime$=7/2 atomic resonance. Because of the high nuclear spin (I=5/2) nature of the system, we observe a complicated structure appears with several vibrational series each following the LeRoy-Bernstein progression. We compare our results with a numerical calculation based on a single channel Movre-Pichler model. We also investigate the magnetic field dependence of the photoassociation spectrum.