Charge Fluctuations in Europium in Metallic EuCu2Si2

摘要: Recoilless-absorption measurements of the 21.6-keV $\ensuremath{\gamma}$ ray ${\mathrm{Eu}}^{151}$ in Eu${\mathrm{Cu}}_{2}$${\mathrm{Si}}_{2}$ reveal an absorption line which has a strongly temperature-dependent isomer shift. The lines fall at neither ${\mathrm{Eu}}^{3+}$ nor ${\mathrm{Eu}}^{2+}$ valence positions, but between. results are interpreted terms fast fluctuations ($\ensuremath{\tau}l3.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ sec) electron between localized $4f$ level and conduction band. difference energy states is found to be about 0.07 eV.