Electronic Absorption Spectrum of Ni II in Cubic Perovskite Fluorides. I

摘要

The fine structure of the spectrum of Ni2+in KNiF3and KMgF3:Ni has been analyzed in terms of the spinmdash;orbit splitting and vibrational intervals using a fourhyphen;parameter crystalhyphen;field approach. The parameters obtained from the analysis differ from the freehyphen;ion values by relatively small amounts, but the differences are not interpretable physically because configuration interaction has been neglected. We find thatDq=698 cmmdash;1, lgr;=mdash;(305ndash;320) cmmdash;1,F2=1520 cmmdash;1,F4=114 cmmdash;1(F4/F2=0.675). For the free ion we find that lgr;=mdash;334 cmmdash;1,F2=1622 cmmdash;1, andF4=116 cmmdash;1by fitting the published values for the 3d8energy levels in our analysis withDq=0.We find that the effects of exchange interaction on the excited state energy levels is small, and that no Jahnmdash;Teller splitting is observed or expected for this crystal. An explanation is offered for temperature changes in the3A2grarr;1Egtransition involving a breakdown of Bornmdash;Oppenheimer separability.