Photodissociation of NH3 at 106-200 nm

The absorption and fluorescence cross sections for NH3 are measured in the 106-200 nm region using synchrotron radiation as the light source. The threshold wavelengths for the production of the NH (b to X) and NH (c to a) emissions from NH3 dissociation are measured and compared with previous measurements. The heat of formation of NH determined from these thresholds agrees well with the value determined from thermochemical data. The process of dissociation of NH3 into NH2(2AL) and H2(S) has a significant quantum yield whose maximum at 134 nm is about twice the NH(c) production yield. All the vibronic levels of the B and C states produce the NH2(2A1) emission, contrary to previous theoretical interpretations.