The infrared spectrum of the I−–D2 anion complex is measured in the D2 stretch region by monitoring production of I− photofragments. The rotationally resolved spectrum consists of two overlapping Σ-Σ subbands, redshifted by ≈58 cm−1 from the free D2 fundamental vibrational band. These subbands are associated with absorptions by I−–D2 complexes containing ortho and para forms of D2. The measured rotational constants are consistent with a 3.79 Å separation between I− and the D2 center of mass, contracting by 0.08 Å when the D2 subunit is vibrationally excited. Spectroscopic data are used to generate effective radial potential energy curves describing the interaction of ortho and para D2 with I− from which the dissociation energies of I−–D2(ortho) and I−–D2(para) are estimated as D0 = 236 and 297 cm−1, respectively. © 2004 American Institute of Physics.