Near‐Infrared d–d Transitions of NiI2, CdI2:Ni2+, and CoI2

Abstract The absorption spectra of NiI 2 , CdI 2 :Ni 2+ , and CoI 2 in the wave‐number region 4000 to 16000 cm −1 are reported. The spectra are interpreted in terms of d‐d transitions of Ni 2+ and Co 2+ ions. Parameters of the electron repulsion, cubic crystal field, and spin‐orbit coupling are estimated. From the latter the transferred spin densities are deduced and compared with Mössbauer data. Birefringence experiments as a function of the temperature show the presence of two phase transitions in niI 2 .