Linear absorption mechanisms in a laser exploded cluster

Summary form only given. The optical properties of a gas of laser-pulse exploded clusters are determined by the time evolving polarizabilities of individual clusters. In turn, the polarizability of an individual cluster is determined by the time evolution of individual electrons within the cluster´s electrostatic potential. These electrons can appear as two distinct species: one confined to the inner cluster core, and the other as an outer halo extracted by the laser. We calculate the linear cluster polarizability using the Vlasov equation. The equilibrium is calculated for a bi-Maxwellian distribution that models both the hot and cold electrons. We then perturb the system to first order in field and integrate the response of individual electrons to the self consistent field following unperturbed orbits. From this we obtain the dipole spectrum. The dipole spectrum depicts strong absorption at frequencies much smaller than omega_p/radic2. Evidence suggests that these peaks result from the onset of a coherent transit time resonance. Absorption also occurs at frequencies higher than omega_p/radic2, suggesting the existence of electro-acoustic waves. Both of these processes appear to be sensitive to the spatial distribution of ions. The effect of noise in the electron phase distribution has also been explored