High-precision detection method of emission signals from a pulsed radio-frequency glow discharge plasma by using a fast fourier transform analyzer

A fast Fourier transform (FFT) analyzer was employed to estimate the emission intensity from a radio-frequency (RF)-powered glow discharge plasma for atomic emission analysis. A bias current induced by a self-bias voltage in the RF plasma was pulsated to modulate the emission intensity, and then the modulated component was selectively detected with the FFT analyzer. This method greatly improved the data precision of the emission intensity, thus contributing to better detection ability. The emission intensity of the Mn I 403.08-nm line in an Fe-0.2 mass % Mn alloy sample could be determined with a relative standard deviation of 0.060%. The 3-sigma detection limit of manganese in Fe-based alloys could be obtained to be 1.6 × 10^-5 mass %, when Mn I 403.08 nm was selected as the analytical line.