The photodissociation of jet-cooled IBr molecules has been investigated at excitation energies just above the threshold for forming ground state I( 2 P 3 / 2 )+Br( 2 P 3 / 2 ) products, using a state-of-the-art ion imaging spectrometer operated under optimal conditions for velocity mapping. The image resolution is sufficient to enable determination of precise, isotope specific values for the ground state dissociation energies D 0 0 (I- 7 9 Br) and D 0 0 (I- 8 1 Br), and thus yield an accurate value for the ground state well-depth, D e =14 798+/-1 cm - 1 . The measured angular distribution of the Br atom product flux formed at energies very close to threshold shows an anisotropy that declines with increasing velocity - an observation rationalised, qualitatively, in terms of breakdown of the axial recoil approximation.