Optical detection of ESR of Tm2+ ions in crystals of the fluorite type in weak magnetic fields

The EPR spectra of a Tm2+ ion in fluorite-type crystals (CaF2, SrF2 and BaF2) were investigated with the aid of a high-sensitivity magnetooptical laser-polarimeter technique in the frequency range of 3-1200 MHz. The specific features of EPR spectroscopy with optical detection in the small magnetic field range, where Zeeman interaction of a paramagnetic ion is less than or comparable with the hyperfine interaction energy are analyzed. The shape of the lines of transition between different hyperfine components of the ground state is investigated, and additional possibilities for determining the nature of line broadening in EPR spectra in the region of nonlinear magnetic splitting are discussed. The sensitivity of the optical technique for EPR detection realized in the investigation is estimated