Field-swept pulsed electron paramagnetic resonance of Cr3+-doped ZBLAN fluoride glass

Field-swept pulsed electron paramagnetic resonance (EPR) spectra of a ZBLAN fluoride glass doped with a low concentration of Cr3+ are obtained using e cho-detected EPR and hole-burning free induction decay detection. We review the utility of the pulsed EPR technique in generating field-swept EPR spec tra, as well as some of the distorting effects that are peculiar to the pul sed detection method. The application of this technique to Cr3+-doped ZBLAN reveals that much of the broad resonance extending from g(eff) = 5.1 to g( eff) = 1.97, characteristic of X-band continuous wave EPR of Cr3+ in glasse s, is absent. We attribute this largely to the variation in nutation freque ncies across the spectrum that result from sites possessing large fine stru cture interactions. The description of the spin dynamics of such sites is c omplicated and we discuss some possible approaches to the simulation of the pulsed EPR spectra.