The dominant Ti3+ trapped electron center in flux-grown RbTiOPO4 (RTP) crystals was characterized using electron paramagnetic resonance and electron–nuclear double resonance (ENDOR). This center was produced during an X-ray irradiation at room temperature when a Ti4+ ion traps an electron and becomes a Ti3+ ion, and was best studied in the 30 to 40K range. The electron paramagnetic resonance spectrum contains a 3-line hyperfine pattern from two nearly equivalent neighboring 31P nuclei, along with hyperfine lines from the 47Ti and 49Ti nuclei. The g matrix, determined from the angular dependence of the electron paramagnetic resonance spectrum, had principal values of 1.819, 1.889 and 1.947. Hyperfine matrices for four 31P nuclei were obtained from the angular dependence of the ENDOR spectrum. The proposed model for this defect was a Ti3+ ion adjacent to an O vacancy at an OT position. Analogies were made to a similar Ti3+ center in KTiOPO4 (KTP) crystals.

EPR and ENDOR Study of an Oxygen-Vacancy-Associated Ti3+ Center in RbTiOPO4 Crystals. Y.Jiang, L.E.Halliburton, M.Roth, M.Tseitlin, N.Angert: Physica B, 2007, 400[1-2], 190-7