| Popis: |
We have measured the electron energy loss spectra of Ca 2 V 2 O 7 in the reflexion mode, at incident energies between 200 and 2400 eV, and the X-ray photoelectron spectra excited by Al K α radiation. The abundant loss structures observed can be correlated with the possible interband transitions, collective oscillations, and excitation of O2s and V3p electrons within the V 2 O 7 4- ion. The gap width and molecular orbital (MO) spread (or splitting) is about l eV larger in the V 2 O 7 4- ion than in its component VO 4 3- ion. Excitation of O2s states, which may occur together with some MO over-gap transitions, displaces the collective oscillations about 7 eV towards lower energies. Deeper V3p electrons are excited with a maximum energy loss some 7 eV above their binding energy. Cross transitions from Ca3p levels into some empty states of the V 2 O 7 4- ion, or direct transitions to available states of the Ca 2+ ion could not be unambiguously identified. The energy dependence of the excitation cross section and of the electron penetration depth results in a significant variation of the relative intensity of various losses over the investigated energy range. |
