High multipole transitions in NIXS: valence and hybridization in 4f systems

TL;DR

This study investigates high multipole transitions in non-resonant inelastic x-ray scattering of rare earth compounds, revealing how multiplet features vary with momentum transfer and hybridization, supported by theoretical modeling.

Contribution

It provides the first detailed experimental and theoretical analysis of multipole scattering in NIXS for 4f systems, highlighting sensitivity to hybridization effects.

Findings

Multiplet features diminish with increasing momentum transfer.

Strong multiplet lines emerge at lower energy transfer, distinct for different 4f initial states.

Hybridization broadens multiplet features, indicating sensitivity to electronic environment.

Abstract

Momentum-transfer (q) dependent non-resonant inelastic x-ray scattering measurements were made at the N4,5 edges for several rare earth compounds. With increasing q, giant dipole resonances diminish, to be replaced by strong multiplet lines at lower energy transfer. These multiplets result from two different orders of multipole scattering and are distinct for systems with simple 4f^0 and 4f^1 initial states. A many-body theoretical treatment of the multiplets agrees well with the experimental data on ionic La and Ce phosphate reference compounds. Comparing measurements on CeO2 and CeRh3 to the theory and the phosphates indicates sensitivity to hybridization as observed by a broadening of 4f^0-related multiplet features. We expect such strong, nondipole features to be generic for NIXS from f-electron systems.