TEMPERATURE-MEASUREMENT FROM SCATTERING SPECTRA OF CLUSTERS - THEORETICAL TREATMENT

Scattering spectra from X-ray, electron or neutron diffraction experim ents are sufficient to describe the phase behaviour of noble gas clust ers and to determine their temperature. Using classical Monte Carlo si mulations combined with optimized data analysis and Path Integral Mont e Carlo calculations as ''idealized experiments'' we obtain scattering spectra of Ar- and Ne-clusters. Starting from the classical and quant um mechanical hypervirial theorems we devise a method to estimate the temperature and the caloric curves (which describe the phase behaviour of the noble gas clusters) directly from these scattering spectra usi ng an interatomic potential function as input. As applications we stud ied for Ar-clusters the effect of different model potentials on the te mperature estimate thus contributing to the intricate question of what experimentally is the temperature of an isolated cluster. For Ne-clus ters we investigate the differences between classical and quantum mech anical treatment.