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.