The vibrational lifetimes of the O-H and O-D stretch modes in the perovskite oxide KTaO3 are measured by pump-probe infrared spectroscopy. Both stretch modes are exceptionally long lived and exhibit a large “reverse” isotope effect, due to a phonon-assisted proton-tunneling process, which involves the O-Ta-O bending motion. The excited-state tunneling rate is found to be 7 orders of magnitude larger than from the ground state in the proton conducting oxide, BaCeO3 [Phys. Rev. B 60, R3713 (1999)]. (Read more)

Three dominant iron centers are studied in the as-grown ⁵⁷Fe-doped single KTaO₃ crystals. For each of the centers, which were labeled as rhombic Fe_Ta³⁺ and two axial Fe-related centers Fe_K³⁺-O_I and (Fe). The... (Read more)