Large Final-State Effects in the Core-Level Electron Energy-Loss Spectra of Vanadium at Low Incident-Electron Energies

Large final-state effects have been observed in the $3p$, $3s$, and $2p$ electron energyloss spectra of vanadium as the incident-electron energy was reduced from 1500 eV to about 50 eV above the core threshold. Changes in the line shapes for the onset of 2p3/2 excitation and changes in measured threshold energies for 2p3/2, $3s$, and $3p$ excitation show the significance of the transition from sudden to adiabatic excitation. Strong excitations due to exchange effects are also observed in the $3p$ spectra at low incident energies.