Laser-induced breakdown spectra in the infrared region from 750 to 2000 mn using a cooled InGaAs diode array detector

Emissions from a laser-induced breakdown spectroscopy (LIBS) plasma were examined in the region from 750 nm to 2000 run. A Nd:YAG laser at 532 nm and 75 mJ per pulse were used to initiate the plasma. The detector was an InGaAs 1024 element diode array cooled to -100 degrees C. An f/4 spectrometer with gratings blazed for this region was used as the dispersive element. Survey spectra of soils, uranium, and other selected samples were taken in air and in a How cell purged with argon at a local pressure of 0.84 X 10(5) Pa. Strong infrared lines of neutral aluminum, carbon, potassium, silicon, sulfur, and uranium, as well as once ionized lines of calcium, were observed out to 1670 mn. For potassium, the detection limits of the infrared (IR) system were compared with those obtained from a standard intensified charge-coupled device (ICCD) spectrometer arrangement, using the 766-770 mn doublet. Detection limits with the IR system were twice as high as those obtained from the ICCD detector.