CARS spectra of NH<sub>3</sub> have been obtained from a commercial catalytic ammonia oxidation plant operating at ∼10 atmospheres (absolute) and 250°C. A purpose-designed ruggedized CARS spectrometer—incorporating a novel dye laser, remote control, and fiber optic signal transfer—is described. A new and simple technique for CARS concentration analysis using polarized beams gave a precision of 5.9% for NH<sub>3</sub> from single-shot spectra under laboratory conditions. Unfortunately, severe beam steering problems were encountered in the full-scale plant; this prevented a quantitative analysis of the spectra obtained. The origins of this problem together with suggestions for overcoming or reducing its effect are given.
William A. England and Ansar Ali, "CARS Spectroscopy of Ammonia in the Laboratory and a Commercial Scale Ammonia Oxidation Plant," Appl. Spectrosc. 42, 1412-1421 (1988)