報文

Quantitative Elemental Analysis of Silicate Rocks by Laser-Induced Plasma Spectroscopy

Takahiro YASUDA, Masahiro MURAKAMI and Mikio KUZUYA

　　A quantitative elemental analysis of silicate rocks was carried out with a laser microprobe analyzer. A Q-switched Nd:YAG laser (90 mJ, 10 ns) was focused on rock samples in an argon atmosphere at reduced pressure, and the emission spectra from laser-induced plasma were measured using time-resolved spectroscopy. The experimental results showed that the maximum spectral line intensity was obtained in argon at approximately 200 Torr, whereas the spectral line-to-background ratio were maximized at around 60 Torr, by observing the laser plasma with a time delay of 0.4 ms. Furthermore, the results of time-resolved spectroscopy of the plasma produced in argon at 200 Torr and 60 Torr indicated that time-resolved measurement of a spectrum in the initial stage of plasma generation (〜1 ms) at a pressure of 60 Torr was effective for improving the slope of the calibration curve. Based on the results, standard rock samples were analyzed for aluminum, magnesium, calcium, titanium and iron, and linear calibration curves with a slope of unity were obtained by measuring spectra with a gate width of 0.6 ms at a delay time of 0.4 ms after the laser pulse in argon at 60 Torr.

Keywords: Laser-induced plasma, time-resolved spectroscopy, argon at reduced pressure, calibration curve, analysis of rocks