Ammonia detection and monitoring with photofragmentation fluorescence

Excimer laser fragmentation-fluorescence spectroscopy is an effective detec tion strategy for NH3 in combustion exhausts at atmospheric pressure and hi gh temperatures. Two-photon photofragmentation of NH3 with 193-nm light yie lds emission from the NW(A-X) band at 336 nm. There are no major interferen ces in this spectral region, and the sensitivity is at the parts per billio n (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 p pb for a 100-shot (1-s) average. This technique could prove useful in monit oring ammonia emissions from catalytic and noncatalytic NOx reduction proce sses involving ammonia injection. (C) 1998 Optical Society of America.