  We present a new spectroscopy technique for studying cold-collision
properties. The technique is based on the association and dissociation of
ultracold molecules using a magnetically tunable Feshbach resonance. The energy
and lifetime of a shape resonance are determined from a measurement of the
dissociation rate. Additional spectroscopic information is obtained from the
observation of a spatial interference pattern between an outgoing s wave and d
wave. The experimental data agree well with the results from a new model, in
which the dissociation process is connected to a scattering gedanken
experiment, which is analyzed using a coupled-channels calculation.
