Time-Resolved Light-Emission Spectroscopy and Ion Current Measurements from Pulsed-Laser-Evaporated Cadmium Plumes

We have investigated the pulsed laser evaporation of elemental Cd targets, with the aim of understanding the velocity distributions in the plumes and the changes which occur under moderate electrical bias. We report detailed kinetic energy distributions of the species in the laser evaporated plumes. In these experiments, frequency doubled, Q-switched pulses of a Nd:YAG laser were used at a 10 Hz repetition rate to generate the plumes. The velocity distributions of individual atomic species were determined by time-of-flight (TOF) light emission spectroscopy, while the time resolved ion/atom currents were measured with a collector above the target. We have simultaneously measured the dependence of the time resolved optical and electrical signals on the electrical bias applied between target and collector. We find that the typical kinetic energies in the plume are on the order of 10-200 eV, while the ionized species travel two to three times faster than the neutral particles. These results provide fundamental information about the physics of the pulsed laser evaporation process, and subsequent evolution of the plume.