Spectroscopic Studies of a Laser-Produced Plasma in Helium

A highly ionized plasma was produced by laser-induced breakdown in helium at a pressure of 360 Torr. Line and continuum emission from the plasma were studied as a function of time and of position along the axis of the laser beam. Plasma parameters were then deduced from Stark widths, line-to-continuum, and line-to-line intensity ratios. The applicability of the various methods used to the case of a rapidly decaying laser-produced plasma is discussed. The decay of the plasma is analyzed and the observed decay coefficients are compared with theoretical calculations.