Frequency-domain techniques offer a powerful means to disentangle overlapping physical processes with distinct characteristic timescales-yet remain underexplored in the context of complex photoluminescent materials. Here, frequency-domain analysis is applied to persistent luminescence (PersL) materials, which exhibit long-lasting emission following excitation due to charge trapping and detrapping processes spanning wide temporal ranges. Using SrAl2O4:Eu2(+),Dy3(+) (SAO:Eu,Dy) as a model system, a general framework is developed for frequency-domain characterization of PersL and reports, for the first time, a direct measurement of the trapping rate in such a material. This approach also enables quantitative assessment of trapping probability, efficiency, and overall PersL performance. This work opens a new pathway for rational optimization of afterglow materials based on mechanistic insights beyond conventional time-domain approaches.