Studies of californium(II) and (III) iodides

Abstract

The compounds CfI 2 and CfI 3 have been prepared in microgram quantities using high-vacuum techniques. These compounds were characterized by both X-ray powder diffraction and optical spectroscopy. Californium diiodide is prepared by H 2 reduction of CfI 3 at elevated temperatures and exhibits two crystalline modifications: the CdCl 2-type rhombohedral structure with a 0 = 7.434 ± 0.011 Å and α = 35.83 ± 0.07°, and the CdI 2-type hexagonal structure with a 0 = 4.557 ± 0.004 Å and c 0 = 6.992 ± 0.006 Å. Optical spectra taken of the samples reveal absorption bands in the wavelength region 300–1100 nm consistent with the presence of Cf(II). Californium triiodide exhibits the rhombohedral BiI 3-type structure with a 0 = 8.205 ± 0.004 Å and α = 55.08 ± 0.01°. This structure is stable up t0 700°C; linear coefficients of thermal expansion were obtained for the temperature range 20–700°C. Optical spectra taken of CfI 3 showed absorption-peak positions consistent with those expected by extrapolation from known CfCl 3 and CfBr 3 peak positions.