Radiation-induced fluorine interstitial atoms in MgF2

The electron spin resonance spectra of the $H$ center and an $H_A$ center have been investigated in Mg${\mathrm{F}}_2$, a rutile-structured material. Both of the centers are ${\mathrm{F}}_2^{-}$ molecular ions in a split-interstitial configuration. The $H$ centers were produced by electron irradiation at temperatures below 35 K and the $H_A$ centers were produced at 77 K. The $H$ center thermally decays in the 55-65-K range while the $H_A$ center decays near 142 K. No intrinsic $V_K$ centers were observed.