  Continuous wave optically and electrically detected magnetic resonance
spectroscopy (cwODMR/cwEDMR) allow the investigation of paramagnetic states
involved in spin-dependent transitions, like recombination and transport.
Although experimentally similar to conventional electron spin resonance (ESR),
there exist limitations when applying models originally developed for ESR to
observables (luminescence and electric current) of cwODMR and cwEDMR. Here we
present closed-form solutions for the modulation frequency dependence of cwODMR
and cwEDMR based on an intermediate pair recombination model and discuss
ambiguities which arise when attempting to distinguish the dominant
spin-dependent processes underlying experimental data. These include: 1) a
large number of quantitatively different models cannot be differentiated, 2)
signs of signals are determined not only by recombination, but also by other
processes like dissociation, intersystem-crossing, pair generation, and even
experimental parameter such as, modulation frequency, microwave power, and
temperature, 3) radiative and non-radiative recombination cannot be
distinguished due to the observed signs of cwODMR and cwEDMR experiments.
