Laser separation of nitrogen isotopes by the IR + UV dissociation of ammonia molecules

The separation of nitrogen isotopes is studied upon successive single-photon IR excitation and UV dissociation of ammonia molecules. The excitation selectivity was provided by tuning a CO₂ laser to resonance with ¹⁴NH₃ molecules [the 9R(30) laser line] or with ¹⁵NH₃ molecules [the 9R(10) laser line]. Isotopic mixtures containing 4.8% and 0.37% (natural content) of the ¹⁵NH isotope were investigated. The dependences of the selectivity and the dissociation yield for each isotopic component on the buffer gas pressure (N₂, O₂, Ar) and the ammonia pressure were obtained. In the limit of low NH₃ pressures (0.5 — 2 Torr), the dissociation selectivity α (15/14) for ¹⁵N was 17. The selectivity mechanism of the IR + UV dissociation is discussed and the outlook is considered for the development of the nitrogen isotope separation process based on this approach.