Laser-Induced Breakdown Spectra in the Infrared Region from 750 to 2000 nm Using a Cooled InGaAs Diode Array Detector

Abstract

Emissions from a laser-induced breakdown spectroscopy (LIBS) plasma were examined in the region from 750 nm to 2000 nm. 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 flow 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 nm. 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 nm doublet. Detection limits with the IR system were twice as high as those obtained from the ICCD detector.

Concentration Dependent Studies on the Laser-Induced Mid-Infrared Emission from KCl-NaCl Tablets

“…Although this result is not as good as LOD values reported for near-IR LIBS measurements [3], it is significant given that mid-IR emissions are usually weaker than those observed in the UV-VIS region. In its debut appearance, the MIR LIBS technique has proven to be a worthwhile compliment to the established UV-VIS LIBS technique.…”

“…For potassium monitored at various near-IR wavelengths, they found detection limits ranging from 0.02 to 0.087 wt%/wt. They also obtained detection limits using IR detectors that were twice as much as obtained with the standard intensified charge-coupled device (ICCD) detector [3].…”

“…Very little work, however, has yet been done on longer wavelength IR LIBS [3]. In particular, no report has yet been made in the literature on the limits of detection for LIBS measurements in the mid-IR region.…”

“…However, the determination of the limit of detection depends on a number of experimental conditions including the wavelength of emission, excitation energy as well as the spectral * E-mail: ooyebola@unilag.edu.ng response of the detector. Radziemski et al [3] studied the detection limits of the near infrared emissions of a number of neutral elements. For potassium monitored at various near-IR wavelengths, they found detection limits ranging from 0.02 to 0.087 wt%/wt.…”

“…Several units of measuring detection limit have been reported but most commonly used are parts per million (ppm) [6] and weight percent per weight (wt%/wt) [3]. Since materials were mixed in mass ratios, wt%/wt was the preferred unit for measuring detection limit in this work.…”