Using Feshbach-optimized photoassociation spectroscopy to determine potential energies for excited electronic states of dimers

Many experiments on ultracold ($<1\,$mK) gases use magnetic-field-induced Feshbach resonances to enhance photoassociation (PA)~[1]. A magnetic field applied to a sample of trapped ultracold atoms induces a Feshbach scattering resonance that can increase the PA rate into bound excited molecular states. We are studying how to use Feshbach resonances in PA spectroscopy~[2] to determine accurate excited-state Born-Oppenheimer potential energies. For ${}^{85}$Rb$_2$ we present calculated resonance properties and energies for excited vibrational states that are inaccessible with conventional PA spectroscopy. \\[4pt] [1] Chin et al., Rev. Mod. Phys. \textbf{82}, 1225~(2010).\\[0pt] [2] Pellegrini et al., Phys. Rev. Lett. \textbf{101}, 053201~(2008).