  Using the satellite structure of the $L_{\gamma1}$ line in non-resonant x-ray
emission spectra, we probe the high-pressure evolution of the bare 4f signature
of the early light lanthanides at ambient temperature. For Ce and Pr the
satellite peak experiences a sudden reduction concurrent with their respective
volume collapse (VC) transitions. These new experimental results are supported
by calculations using state-of-the-art extended atomic structure codes for Ce
and Pr, and also for Nd, which does not exhibit a VC. Our work suggests that
changes to the 4f occupation are more consistently associated with evolution of
the satellite than is the reduction of the 4f moment. Indeed, we show that in
the case of Ce, mixing of a higher atomic angular momentum state, driven by the
increased hybridization, acts to obscure the expected satellite reduction.
These measurements emphasize the importance of a unified study of a full set of
microscopic observables to obtain the most discerning test of the underlying,
fundamental f-electron phenomena at high pressures.
