### M$sub 4$ $sub 5$ spectrum of Ce and the $gamma$--$alpha$ phase transitionM$sub 4$ $sub 5$ spectrum of Ce and the $gamma$--$alpha$ phase transition

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 Author Ottewell, D. ♦ Stewardson, E. A. Source United States Department of Energy Office of Scientific and Technical Information Content type Text Language English
 Subject Keyword Physics (Atomic & Molecular)-Atomic & Molecular Properties ♦ Metals, Ceramics, & Other Materials-Metals & Alloys-Properties, Structure & Phase Studies ♦ CERIUM FLUORIDES- ABSORPTION SPECTRA ♦ CERIUM OXIDES- ABSORPTION SPECTRA ♦ CERIUM- PHASE TRANSFORMATIONS ♦ HYSTERESIS ♦ LOW TEMPERATURE ♦ MEDIUM TEMPERATURE ♦ SUPERLATTICES Abstract Absolute absorption coefficients in the region of the M/sub 4/ and M/sub 5/ edges are presented for cerium in CeF/sub 3/, CeO/sub 2/, and in the metal. Strong line absorptions (3d yields 4f) occur to the low energy side of weak M/ sub 4/ and M/sub 5/ edges.'' At each edge'' the absorption passes through a weak broad peak attributed to transitions into a band of higher f states. The spectra of CeF/sub 3/ and the metal at room temperature are structurally similar but differ clearly from the quadrivalent oxide. A shift to higher energy is found for both absorption lines and edges in the sequence fluoride- oxide--metal at room temperature. On cooling the evaporated metal absorption foil ( gamma phase) to 77 deg K both M/sub 4/ and M/sub 5/ line profiles change into forms accurately resolvable into a combination of trivalent (CeF/sub 3/ like) and quadrivalent (CeO/sub 2/ like) curves, suitably displaced in energy, in the proportions 59% to 43%, respectively. This is interpreted as evidence for the transfer of localized 4f electrons from some of the 3+ ions of the gamma phase when the gamma -- alpha transformation occurs. The line structure exhibits hysteresis and reverts to that of the original gamma phase after repeated cycling between 77 deg K and room temperature. The possibility of superlattice structure in alpha -cerium is discussed. (auth) Educational Use Research Learning Resource Type Article Publisher Date 1973-10-01 Publisher Place United Kingdom Journal J. Phys., B Organization Univ. of Leicester, Eng.