Excitation spectrum and dynamic structure function of 4He clusters

We compute the collective excitations, transition densities, and the dynamic structure function of 4He droplets at zero temperature using a generalized Feynman ansatz for the excitation function. The theory uses as inputs the exact ground state, one- and two-body densities sampled by a second order Diffusion Monte Carlo algorithm. The dynamic structure function appears to be dominated by the zero sound excitation and its modulation by finite size effects.