An analysis of the structured continuum fluorescence (280–390 nm), arising from excitation of IBr at 180 nm, 193 nm and 200 nm, is reported. The fluorescence originates from high vibrational levels of theE(0+) state (v′ ≈ 110–205) and terminates in the continuum of the ground electronic state. TheEstate is quite tightly constrained in the region 3.1–4.8 Å by the Rittner potential and known RKR points, but detailed fitting of the interference structure provides additional information about the ground state beyond 2.9 Å. The transition dipole moment appears to pass through a broad maximum in thisRrange.