Nm Khaidukov

Electron paramagnetic resonance spectroscopy of Cr3+ in hexagonal Cs2NaGaF6 crystals.

Powder samples of hydrothermally grown Cr 3+ -doped Cs 2 NaGaF 6 crystals have been investigated with electron paramagnetic resonance spectroscopy at X - (9.5 v GHz) and Q -band (34 v GHz). Analysis of the spectra clearly demonstrates that there are two distinct Cr 3+ centres in the Cs 2 NaGaF 6 crystal, having nearly identical g factors, but differing largely from the viewpoint of their zero field splitting. By using the 53 Cr hyperfine spectra observed with electron nuclear double resonance spectroscopy, it is deduced that these centres have opposite signs for the zero field splitting. The spectroscopic properties of the Cr 3+ centres in the isostructural Cs 2 NaGaF 6 and Cs 2 NaAlF 6 crystals are compared and discussed.

K{sub 2}YF{sub 5} crystal symmetry determined by using rare-earth ions as paramagnetic probes

The electron paramagnetic resonance angular dependences for Gd{sup 3+} and Ce{sup 3+} centers in K{sub 2}YF{sub 5} crystals show that the Y{sup 3+} site has monoclinic C{sub h} symmetry in these crystals. This site symmetry is compatible with the crystal structure having the Pnam space group. From the zero-field splitting parameters of the Gd{sup 3+} center, it is deduced that the symmetry of the Y{sup 3+} sites is close to trigonal around the b axis, distorted by the overall orthorhombic symmetry of the crystal structure. This information is required for the identification of radiation-induced centers in this material, which shows favorable properties for applications as thermoluminescent dosimeter.