Characteristics of the evolution of a plasma jet during the irradiation of a metal surface by a pulsed XeCl laser

Results of experiments in which various metal targets were irradiated at an angle of 10 deg by 0.3-J, 20-ns pulses of a XeCl laser are reported. In addition to two regions of plasma evolution at the metal surface noted in an earlier study (Kagawa et al., 1983), a third region is identified where the plasma has the shape of a narrow core normal to the surface. At 1-2 mm from the surface, the core contains various metal ion lines. The spectrograms of the jet do not contain any lines of the atoms or ions of the gas surrounding the target (e.g., air, helium, or argon), indicating that the breakdown occurs only in the expanding metal vapors and not in the buffer gas.