Excitation-energy-dependent features in the continuum spectrum of cerium near theMαandMβx-ray emission lines

Abstract

M-series x-ray emission spectra from cerium have been recorded for near-threshold electron excitation.For incident electron energies near the Mv and Miv inner-shell ionization energies, the spectra are dominated by intensity resonances of structures which are part of the continuous spectrum near its high-frequency limit. The intensity and position dependencies of the resonating structures are presented and are interpreted as arising from resonances in the cross sections for scattering electrons into empty 4f levels. No such resonances mere observed for excitation energies near the M,«and M" inner-shell ionization energies.

Polarizational bremsstrahlung in non-relativistic collisions

“…This happens, in particular, when the photon energy lies within the region of a giant dipole resonance of the photoionization cross section of a many-electron atomic subshell [111]. For the first time wide maxima in the emission spectra were observed experimentally in electron scattering from (solid) Ba, La and Ce [112,113]. Later these were explained theoretically [16] by relating the maxima to the virtual excitations of the 3d-subshell electrons.…”

Application of soft x-ray appearance potential spectroscopy to light lanthanides, 4d transition metals, and insulators

“…The x-ray emission data suffers heavily from self-absorption effects and inspection of the data (39) shows close correspondence between emission and absorption features. As for La, the isochronat results (122) show low energy satellites. The la results suggested that these were not due to seli=absorption.…”

“…The la results suggested that these were not due to seli=absorption. They aie attributed to resonant scattering into empty 4f states which are apparent ly below Bp since they occur below the and einission peaks (122). are above This doss not seem to explain the isoehroiiat satellites, since the average separation between the satellite and min peak is 2.5 eV for La and 2.7 eV for Ge, This means that the 4f states are the same distance above B for both La and Ce, Since the SVTL (122) spectra indicate P that this is not the case, we conclude that the satellites are not related to the 4f states in the manner suggested.…”

“…This correspondence las been made on the assumption that our peaks should lie above the optical peaks for two reasons. First, the La results indicated such an analysis might also apply to Ce, Second, Chamberlain et al (122) have made a series of studies on Ce, similar to their La studies (113)» which suggest a peak in the density of states about 2.7 eV above E , These results from SWL F measurements, and the appearance of a low energy satellite about 2,5 eV below the Ma, and emission lines, prompted the assignments in Table 7,…”

Application of soft x-ray appearance potential spectroscopy to light lanthanides, 4d transition metals, and insulators

“…(122) were used to represent the N+l-particle density of states on neighboring atoms which is probed by the scattered incident electron in the non^interacting picture. The absorption coefficient data of Haensel et al(101) were used to represent the density of final states on the excited Ge ion.…”