Optically-detected radiofrequency studies of level anticrossings in phosphorescent crystals

Abstract

Strong radiofrequency transitions between pairs of anticrossing magnetic sublevels of 3(n, π*) benzophenone and three of its isotopically-labeled derivatives in the deep trap host 4,4′-dibromodiphenylether have been observed using optical detection of magnetic resonance methods. An analysis of the frequency dependence of the positions and intensities of these transitions over the range 0.1–500 MHz provides estimates of the magnitudes of the perturbations V which are responsible for both level-anticrossing (LAC) and cross-relaxation (CR) effects in these systems. By comparing the results for different molecules, it is shown that LAC effects are caused by a combination of off-diagonal intramolecular hyperfine and Zeeman terms whereas CR effects are caused by off-diagonal intermolecular hyperfine terms. Typically, V LAC ≥ 10 V CR; hence, the degree of mixing which is associated with each effect is significantly different.