“…This technique can identify the existence states of hydrogen isotopes in metal oxides [22], because O-H, which is a major chemical form of hydrogen isotopes, exhibits multiple IR absorption peaks reflecting the surrounding conditions, such as the proximate existence of a defect. In the case of Li 2 O, several O-D peaks have been reported both on the surface [23,24] and in the bulk [25][26][27][28], and some of them have been assigned to O-Ds interacting with point defects [24,26]. In the present study, the IR absorption analysis was combined with the ion implantation technique, and an in situ measurement was performed during 3 keV D þ 2 irradiation.…”