Optical enhancements and applications of rapid atomic emission spectrometry acousto-optic deflector background correction

Abstract

A glass acousto-optic deflector (AOD) is mounted in a 0.5 m spectrometer for atomic emission background correction. The system allows sequential and rapid observation of adjacent wavelengths for 'on' and 'off' atomic line background correction. Particular attention is directed to optical masking and data acquisition. While AOD components slightly degrade spectroscopic resolution, proper optical masking minimizes this problem and enhances AOD diffraction efficiency. Conversely, reduction of light throughput by masking forces a compromise in minimal useful aperture diameters. Representative atomic spectra with a neon hollow cathode lamp are presented. Utilizing appropriate AOD masking arrangements produced an increase in observed neon line widths to 0.14 nm from the 0.09 nm widths observed in the absence of the AOD. While the acousto-optic has the capability to alternate observed wavelengths in the 100 kHz range, the 3000 Hz upper frequency limit is a function of the current computer manipulation software. The best signal-to-noise ratios were obtained at higher sampling rates. Background correction was performed with a microwave-induced plasma atomic emission source. Spectral characterizations were obtained with the 425 nm scandium emission line, the sodium doublet near 589 nm and the chromium triplet in the 427 nm region. Calibration plots were obtained with solution nebulization and electrothermal vaporization. Time–detector response profiles are illustrated for electrothermally vaporized analytes.