Emission of excited copper atoms in laser-produced erosion plasmas

The distribution of emission from excited states of a copper atom in erosion plasmas formed in vacuum by the action of neodymium laser pulses with a power density of (3–5)×108 W/cm2 on a copper target is studied. Averaged spectra and oscillograms of emission of Cu I lines were recorded in a region of 210–600 nm. Resonant lines of Cu I, lines of cascade transitions to resonant levels of Cu I, and lines from shifted levels of a copper atom are shown to possess the highest intensity. Oscillograms of emission at Cu I transitions have two peaks, which may be associated with two phases of surface evaporation of copper: under the action of a Nd3+:YAG laser pulse and radiation of the core of an erosion plasma plume. The relationship between the intensities of peaks in oscillograms of emission of Cu I lines points to the presence of a considerable cascade contribution to the population of the resonant states of Cu I and self-absorption of resonant lines of a copper atom at the first stage of evaporation of a copper target.