Doppler-Free Spectrum of the Barium 1 S 0 −1 P 1 Transition by Degenerate Four-Wave Mixing Using an Air/Acetylene Flame

Abstract

Doppler-free flame spectrometry based on resonant degenerate four-wave mixing (D4WM) is shown to be an effective analytical tool for the determination of barium at high spectral resolution. Optical phase conjugation is produced in an air/acetylene flame, resulting in an optical signal that is a coherent time-reversed replica of the probe beam. The degenerate four-wave mixing spectrum of barium for the 6s^{2 1}S₀-6s6p ¹P₁ transition at 18,060.19 cm⁻¹ is collected with a linewidth of 0.08 cm⁻¹ (FWHM) with the use of a convenient continuously flowing atmospheric-pressure flame atomizer. A preliminary detection limit of 5 μg/mL barium, while a Doppler-free linewidth is maintained at 0.08 cm⁻¹, is reported.