Evolution of the spin-orbit excitation with increasing Kondo energy in ${\mathrm{CeIn}}_{3\mathrm{-}\mathit{x}}$${\mathrm{Sn}}_{\mathit{x}}$

Neutron scattering measurements on ${\mathrm{CeIn}}_3$ show the ${}_{}{}^2{}_{}{}^{}$${\mathit{F}}_{5/2}$${\to }^2$${\mathrm{F}}_{7/2}$ spin-orbit excitation at ∼273 meV of half-width Γ∼18 meV, while ${\mathrm{CeSn}}_3$ reveals a broad excitation (Γ∼70 meV) at a significantly higher energy (∼345 meV). With increasing Sn content x, hence increasing Kondo energy, the series of compounds ${\mathrm{CeIn}}_{3\mathrm{-}\mathit{x}}$${\mathrm{Sn}}_{\mathit{x}}$ show a progressive upward energy shift of the excitation. This is accompanied initially by a collapse of the crystal-field splitting and beyond x∼1 by a concomitant increase in width.