Inelastic Diffraction and Spectroscopy of Very Weakly Bound Clusters

We study the coherent inelastic diffraction of very weakly bound two body clusters from a material transmission grating. We show that internal transitions of the clusters can lead to new separate peaks in the diffraction pattern whose angular positions determine the excitation energies. Using a quantum mechanical approach to few body scattering theory we determine the relative peak intensities for the diffraction of the van der Waals dimers (D_2)_2 and H_2-D_2. Based on the results for these realistic examples we discuss the possible applications and experimental challenges of this coherent inelastic diffraction technique.