Spatial and temporal evolution of argon sparks.

Optical emission spectroscopic studies of laser-created argon sparks are carried out. Pulses of 532 nm and 8 ns from a frequency-doubled Nd:YAG laser are used to create an argon spark at 1 atm. Gated photography of 2 ns is used to investigate spark evolution at early times. Electron temperature and density measurements are made from the spectral data. The Stark broadening of emission lines is used to determine the electron density, and the Boltzmann plot of the singly ionized argon-line intensities is exploited for determination of the electron temperature. The dependence on electron temperature and density on different experimental parameters, such as distance from the focal point, delay time after the initiation of the spark, and laser energy, are discussed.