Isotopically selective dissociation of small molecules exposed to pulsed CO2 laser radiation

It is found that the multiphoton dissociation yield of small, particularly light, molecules (HFCO/DFCO, CHF₃/CDF₃, SiH₄, ¹²CF₃Br/¹³CF₃Br, CF₃I) may be increased many times by adding appreciable quantities of buffer gases (Ar, He, NO). In this respect, multiphoton dissociation of small molecules differs from the dissociation of polyatomic molecules (SF₆, C₆F₆, CF₃COCF₃) for which the dissociation yield decreases when buffer gases are added. The effective isotopic selectivity of the dissociation of small molecules may either decrease or increase when buffer gases are added depending on the isotope shift, the laser radiation frequency used, and on the pressures of the isotopic molecule mixture and the buffer gas.