A Quantitative Analysis of Neodymium and Samarium at Low Pressure by Laser-Induced Breakdown Spectroscopy

摘要

In a quantitative analysis by laser-induced breakdown spectroscopy (LIBS), the minimization of white noise is a very important problem. The LIBS measurement was carried out to derive an optimized measurement condition with minimum white noise at low pressure. The thinner the ambient gas becomes, the larger the size of the plasma sphere becomes. The growth of the plasma started at a gas pressure of 15.0 Torr, and the plasma was slightly distinguishable by the inner sphere and the outer sphere at a pressure of 900 mTorr. It was clearly distinguishable at a pressure of 600 mTorr, and the sphere size was about 20.0 mm at this pressure. The measurement of the plasma was taken at a 6.0-mm distance, in the direction of a plasma sphere, from a sample. This location belongs to the outer sphere region in the plasma. Four Nd and Cu mixed samples and five Sm and Cu mixed samples that had mutually different components were prepared in an arc melting furnace at 3000 deg C, starting with a homogeneously mixed powder form of Nd, Sm, and Cu. The measurement was performed after 50 laser ablations under the same conditions and was repeated 10 times. The result was satisfactory with a normal distribution, and the signal intensity was found to be proportional to the concentration of the sample. The linear regression analysis was carried out, and then the R~(2) values for Nd and Sm were determined to be 0.9913 and 0.9535, respectively.