Diffraction and vibrational dynamics of large from He atom scattering

The vibrational dynamics of large Arn clus- ters from n=30 to n=4500 is investigated by measuring the energy loss of He atoms in a high resolution scatter- ing experiment. The clusters are generated by adiabatic expansion through conical nozzles and contain a distri- bution of cluster sizes. The He supersonic nozzle beam provides a resolution of better than 1 meV. The results are compared with calculated spectral density functions for single cluster sizes and bulk phonon spectra.