[Study on the electron density distribution of laser-induced air plasmas]

An 1. 06 microm Nd : YAG laser beam (energy: -500 mJ/pulse, pulse width: 10 ns, repetition rate: 30 Hz) was focused by a conical lens, and a column of laser-induced air plasmas (LIAP) came into being. The LIAP column, about 8 cm of long and 5 cm in maximal diameter, was studied by spectra measurement. The spectra of the LIAP column at different position were measured in the directions both perpendicular and parallel to the laser propagation respectively. From these data, the electron densities of the LIAP were evaluated. The experimental results indicate that the LIAP formed in an olivary shape, i. e. , symmetrical in the vertical direction but unsymmetrical in the horizontal direction, and the maximal electron density is about 10(18) cm(-3). The spatial distributions of atoms, molecules and ions in different states in the LIAP were also discussed, and provide clues for discovering the microstructure of LIAP.