The infrared photodissociation spectra of Ar dimer ions have been obtained at several wavelengths with a line tunable CO2 laser. The dimer ions were produced by high energy electron impact ionization near or at the nozzle orifice of a supersonic expansion. When the electron beam is focused several millimeters from the nozzle, and the laser polarization is parallel to the dimer ion beam, the product Ar+ kinetic energy spectra exhibit structure, with a spacing of 117 cm(-1). However, when the ions are produced by focusing the electron beam directly onto the nozzle, the structure largely disappears. Analysis of the results indicates that the transition is a bound to continuum transition, and that the observed spacing is associated with vibrational levels of the first excited Ar2+I(3/2)g state.