Optical diagnostics of laser-generated indium plasma

The optical emission from a plasma torch formed at the surface of an indium target under the action of laser radiation with a wavelength of lambda = 1.06 mu m and a power of (3-5) x 10(8) W/cm(2) was studied. Wide-scan (200-600 nm) emission spectra, relative intensity distributions of the emission In(I) and In(II) lines, and the dynamics of the emission from the plasma of the nucleus of the erosion torch were measured. The total emission spectrum of the plasma represents In(I) and In(II) lines on a continuous emission background. The most intense lines at 451.1, 410.2, 325.8 (6), and 271.1 (4) nm correspond to the upper excited states with energies in the range from 3.02 to 4.84 eV. The principal mechanism of occupation of the excited states of indium atoms and ions in the laser-generated plasma is the two-electron recombination. The emission duration for the In(II) transitions in plasma of the laser torch nucleus does not exceed 80-100 ns, while that for the In(I) transitions amounts to 400-700 ns. The corresponding upper limits of the recombination times for In(III) and In(II) ions are 50 and 500 ns, respectively. (C) 2000 MAIK "Nauka/Interperiodica".