Measurements of aluminum and hydrogen microplasma.

We report time-averaged and time-resolved emission spectra subsequent to laser-induced optical breakdown of aluminum in laboratory air and in hydrogen gas. The microplasma generated by nominal 10 ns IR laser radiation shows Stark-broadened and shifted atomic lines. An analysis of the H(alpha) and H(beta) Balmer series lines and selected aluminum lines allows one to determine electron number density in the range of 0.01 - 10 x 10(18) cm(-3) early in the plasma decay. Atomic and molecular features are investigated for diagnostic applications in laser material processing.