Analytical capability of the plasma induced by IR TEA CO2 laser pulses on copper-based alloys

The applicability of a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 mu m and 100 ns pulse length (initial spike), induced plasma under reduced air pressure for spectrochemical analysis of bronze and brass samples was investigated. The plasma consisted of two clearly distinguished and spatially separated regions and expanded to a distance of about 10 mm from the surface. The elemental composition of the samples was determined using a time-integrated space-resolved laser-induced plasma spectroscopic (TISR-LIPS) technique. Sharp and well-resolved spectral lines mostly atomic, and negligibly low background emission, were obtained from a plasma region 7 mm from the target surface. Good signal to background and signal to noise ratios were obtained. The estimated detection limits for the trace elements Mg, Fe, Al and Ca were in the order of 10 ppm in bronze and around 50 ppm in brass. Damage on the investigated samples induced by TEA CO2 laser radiation was negligible.