Ammonia detection and monitoring with photofragmentation fluorescence

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Abstract
Excimer laser fragmentation-fluorescence spectroscopy is an effective detection strategy for NH3 in combustion exhausts at atmospheric pressure and high temperatures. Two-photon photofragmentation of NH3 with 193-nm light yields emission from the NH(A– X) band at 336 nm. There are no major interferences in this spectral region, and the sensitivity is at the parts per billion (ppb) level. Quenching of the NH(A) state radical by the major combustion products is measured and does not limit the applicability of the detection method. Detection limits in practical situations are of the order of 100 ppb for a 100-shot (1-s) average. This technique could prove useful in monitoring ammonia emissions from catalytic and noncatalytic NOx reduction processes involving ammonia injection.