PHYSICS Understanding Feshbach molecules using radio-frequency spectroscopy Ultracold Fermi gases provide versatile and lexible setings for molecular interactions and reaction dynamics in quantum regimes.Recently,Lianghui Huang and colleagues created weakly bound Feshbach molecules from the two spin components of40K atomic Fermi gas.hey then investigated the radiofrequency(RF)spectra of the weakly bound molecules and from that obtained the magnetic-ield-dependent binding