Giant 4p-quadrupole resonances in the Rare Earths

X-ray absorption of Ce obtained by partial secondary yield, is compared with previously obtained electron-energy loss measurements in reflection mode. The absence of a strong feature below 4p3/2 threshold in photon absorption provides confirmation that the peak in EELS is nondipole in character. Theoretical analysis supports interpretation in terms of a p-f giant quadrupole resonance, a result which broadens the analogy between giant resonances in atomic and nuclear physics