Photodecomposition of MnO4-: A theoretical study

The electronic and geometrical structures of the ground stated and low-lyin g isomers of MnO4 and MnO4- have been calculated as a function of spin-mult iplicities by using the molecular orbital theory based on generalized gradi ent approximation to the density functional formalism. Total energies of is omers are used for evaluating the energetics of the MnO4- decay through var ious fragmentation channels. Two primary channels were found depending on t he energy of photons. The preferred photofragmentation channel, accessible with approximate to 2 eV photons, is found to involve an initial excitation of the ground-state MnO4- anion into its peroxo isomer followed by subsequ ent excitations into a superoxo form. Photodetachment of an extra electron from this superoxo isomer anion leads to the formation of a neutral superox o isomer of MnO4, which, in turn, dissociates to MnO2 + O-2. Excitations of the anion peroxo isomer into biperoxo isomer are also possible with 3.7 eV , photons and the latter could dissociate spontaneously to MnO2- + O-2. A n umber of other decay channels are accessible with low-energy photons, but t heir intensities are expected to be Low because these require flipping the spin of one or more electrons.