Non-mass-dependent isotope separation in the photodissociation of water and ozone

The author presents the results of state-to-state photodissociation dynamics experiments that reveal isotopic fractionation that is independent of mass. In the case of the photofragmentation of ozone the mass-independent fractionation is the result of electronic non-adiabatic effects in the exit channel. These lead to equal 17O and 18O enrichment of the O2 (3Σg) + O(3P) fragments and equal 17O and 18O depletion of the O2 (1Δg) + O(1D) fragments. In the photodissociation of water he shows that Franck-Condon effects can produce H/D fractionation that is independent of mass. Experiments with the HOD water isotopomer show that excitation of the fundamental of the OH stretch vibration can lead to production of H + OD fragments with much greater probability than D + OH fragments. For the same photodissociation wavelength excitation of the OD stretch does not enhance either fragment channel. Each of the processes he observes and characterizes are possible and even probable in chemical systems occurring in nature, and can be the source of observable non-mass-dependent isotope fractionation