<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Ce</mml:mi><mml:mi/><mml:mn>4</mml:mn><mml:mi>f</mml:mi></mml:math>electron in Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2.1</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2.4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Pd</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Rh</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, and Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ru</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: A photoemission study using synchrotron radiation
Abstract
We present a photoemission study of the $\mathrm{Ce}4f$ electron in materials which range from the localized, trivalent ($4{f}^{1}$) compounds Ce${\mathrm{H}}_{2}$ and Ce${\mathrm{Al}}_{2}$ to the reportedly tetravalent ($4{f}^{0}$) compounds Ce${\mathrm{Rh}}_{3}$ and Ce${\mathrm{Ru}}_{2}$. Using synchrotron radiation in the photon energy range of $10\ensuremath{\le}h\ensuremath{\nu}\ensuremath{\le}140$ eV, we compare the valence-band emission of the Ce compounds with that of the analogous La compounds, paying particular attention to resonant behavior near the $4d\ensuremath{\rightarrow}4f$ transition threshold. In addition, we use the partial photoelectron yield as an indicator of the degree of $4f$ localization as well as occupation. We find no evidence of a change in $4f$ occupation across the series Ce${\mathrm{H}}_{2.1}$\ensuremath{\rightarrow}Ce${\mathrm{Ru}}_{2.}$ Instead, we find an increase in the width of the $4f$ emission and an increase in the effect of the $4f$ electron on the remaining band states. We conclude that the apparent valence changes in these particular compounds are due primarily to hybridization effects, in agreement with recent band-structure calculations.
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