Abstract

It is shown that the technique of intermodulated fluorescence can effectively correct for scattering problems in analytical flame fluorescence spectroscopy. When two laser beams, amplitude-modulated at different frequencies <i>f</i>₁ and <i>f</i>₂ and counterpropagated colinearly throughout an atomizer, are tuned to the absorption transition of the element of interest, non-linear mixing of the fluorescence signal results, due to saturation effects. By extraction of the signal at the sum or difference frequency, <i>f</i>₂ ± <i>f</i>₂, the linear scattering component of the spectrum can be essentially eliminated. This has been demonstrated for a sodium solution nebulized in a premixed, laminar, argon-oxygen-hydrogen flame. Because the modulation signal can be observed only at the intersection volume between the two beams, this technique constitutes a powerful tool for spatially resolved combustion diagnostics.

Comparison of nanosecond and picosecond excitation for interference-free two-photon laser-induced fluorescence detection of atomic hydrogen in flames

Waruna D. Kulatilaka, Brian D. Patterson, Jonathan H. Frank, and Thomas B. Settersten
Appl. Opt. 47(26) 4672-4683 (2008)

Comparison of nanosecond and picosecond excitation for two-photon laser-induced fluorescence imaging of atomic oxygen in flames

Jonathan H. Frank, Xiangling Chen, Brian D. Patterson, and Thomas B. Settersten
Appl. Opt. 43(12) 2588-2597 (2004)

Three-photon-excited laser-induced fluorescence detection of atomic hydrogen in flames

Ayush Jain, Yejun Wang, and Waruna D. Kulatilaka
Opt. Lett. 44(24) 5945-5948 (2019)

Doppler-free laser-induced fluorescence of oxygen atoms in an atmospheric-pressure flame

Mark J. Dyer and David R. Crosley
Opt. Lett. 14(1) 12-14 (1989)

Detection of iron atoms by emission spectroscopy and laser-induced fluorescence in solid propellant flames

G. Vilmart, N. Dorval, M. Orain, D. Lambert, R. Devillers, Y. Fabignon, B. Attal-Tretout, and A. Bresson
Appl. Opt. 57(14) 3817-3828 (2018)