The optical properties of laser-induced plasma generated from solid (Al alloy) and liquid (Mn, Cr, Mg, or Ti solutions) samples expanded across an external, steady magnetic field have been studied by atomic-emission spectroscopy. Various line emissions obtained from the constituents of the Al alloy and of the aqueous solution show an enhancement in intensity in the presence of an ~5-kG magnetic field. The enhancement of the signal was nearly a factor of 2 for the minor constituents of the solid samples and a factor of 1.5 for the elements in liquid phase. Temporal evolution of the emission from the solid sample showed maximum enhancement in emission intensity at 3–10-μs time delay after plasma formation in the laser energy range 10–50 mJ. However, for the liquid sample the maximum signal was for a gate delay of 3–25 μs in the energy range 50–200 mJ. This enhancement in the emission intensity was found to be due to an increase in effective density of the plasma as a result of magnetic confinement when the plasma cooled after expansion. This enhanced emission was due to an increase in the rate of radiative recombination in the plasma.
© 2003 Optical Society of America
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(140.3440) Lasers and laser optics : Laser-induced breakdown
(300.2140) Spectroscopy : Emission
(300.6210) Spectroscopy : Spectroscopy, atomic
(300.6360) Spectroscopy : Spectroscopy, laser
Virendra N. Rai, Awadhesh K. Rai, Fang-Yu Yueh, and Jagdish P. Singh, "Optical Emission from Laser-Induced Breakdown Plasma of Solid and Liquid Samples in the Presence of a Magnetic Field," Appl. Opt. 42, 2085-2093 (2003)