Optical detection of a hydrogen complex responsible for theFphosphorescence in thermochemically reduced MgO crystals

A hydrogen complex denoted as [${\mathrm{H}}_{\mathrm{x}}$ ${\mathrm{}}^{\mathrm{-}}$ ${]}^0$ has been detected using optical-absorption techniques. The local mode of the hydrogen in the anion sublattice resonates at 1037 ${\mathrm{cm}}^{\mathrm{-}1}$ and a broad absorption peaking at 400 nm characterizes the electronic transition of this complex. It is shown to be the predominant electron trap involved in the photoconversion process of F→$F^{+}$ centers. It is metastable at room temperature, giving rise to the F phosphorescence (the thermoluminescence which peaks at 260 K). We further demonstrate that this complex is not the defect identified previously as an ${\mathrm{H}}^{2\mathrm{-}}$ ion by electron paramagnetic resonance at low temperature.