  The effect of exchange interactions within spin pairs on spin-dependent
transport and recombination rates through localized states in semiconductors
during coherent electron spin resonant excitation is studied theoretically. It
is shown that for identical spin systems, significant quantitative differences
are to be expected between the results of pEDMR/pODMR experiments were
permutation symmetry is the observable as compared to pESR experiments with
polarization as the observable. It is predicted that beat oscillations of the
spin nutations and not the nutations themselves dominate the transport or
recombination rates when the exchange coupling strength or the field strength
of the exciting radiation exceed the difference of the Zeeman energies within
the spin pair. Furthermore, while the intensities of the rate oscillations
decrease with increasing exchange within the spin pairs, the singlet and
triplet signals retain their relative strength. This means that pEDMR and pODMR
experiments could allow better experimental access to ESR forbidden singlet
transitions which are hardly or not at all accessible with conventional pulsed
electron spin resonance spectroscopy.
