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

Ammonia-d3 of differing 14N/15N 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 15N, 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 N2 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.