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.