  The photoassociation (PA) of rubidium dimer (Rb2) in a dark magneto-optic
trap (MOT) is studied using atom-cavity collective strong coupling. This allows
non-destructive detection of the molecule formation process as well as rapid
and repeated interrogation of the atom-molecule system. The vacuum Rabi
splitting (VRS) measurements from the bright MOT are carefully calibrated
against equivalent measurements with fluorescence. Further loading rates in
dark MOT are determined using VRS. This method provides a reliable, fast, and
non-destructive detection scheme for ultracold molecules when the atoms are
non-fluorescing using the free atoms coupled to a cavity.
