Enrichment of nitrogen-15 by the direct laser photolysis of ammonia-d3 in the transition

Ammonia-d 3 of differing 14 N/ 15 N ratios has been photolysed in the [Formula: see text] transition using a narrow-band-width, frequency-doubled, pulsed dye laser. At specific excitation wavelengths, chosen by absorption spectroscopy, the product nitrogen is enriched in 15 N, a maximum enrichment factor of 4.8 being attained. The initial isotopic selectivity of excitation is largely retained in the nitrogen product, even though the primary photodissociation forms free radicals and N 2 is formed only after a sequence of secondary reactions. Quantum yields of nitrogen and hydrogen formation have been measured at very low conversions as a function of the time of irradiation. The initial yield of nitrogen appears to be zero and that of hydrogen 0.25.