A. Saar

Ti 2p and O 1s X-ray absorption of TiO2 polymorphs

Abstract We present and discuss the Ti 2p and O 1s X-ray absorption spectra (XAS) and resonant photoelectron emission spectra (RPES) of the various polymorphic forms (TiO2-II, rutile and anatase) of TiO2. The largest differences between the Ti 2p XAS of polymorphs of TiO2 are observed in the region of the double peak structure of the L3 edge. A strong delocalization of the excited 3d electron in this region is concluded from the RPES at the L3 threshold of Ti. The differences in XAS are attributed to increasing strength of the crystal field caused by delocalization of the excited 3d electron.

Multi-atom resonant photoemission in transition metal chlorides

Abstract Recently multi-atom resonances in photoemission of transition metal oxides were observed by Kay et al. [A. Kay, E. Arenholz, S. Mun, F.J. Garcia de Abajo, C.S. Fadley, R. Denecke, Z. Hussain, M.A. Van Hove, Science 281 (1998) 679]. We present the results of a systematic study of multi-atom resonant photoemission in transition metal chlorides. We measured the intensity of the chlorine 2p photoelectron line excited around the metal 2p photoabsorption edge of the transition metal compounds MnCl 2 , CrCl 2 , and VCl 2 as well as of the ionic solid KCl. Our experimental results show that the intensity of Cl 2p photoelectron lines enhance by about 29% for MnCl 2 , 21% for CrCl 2 , 17% for VCl 2 and 11% in the case of KCl at the metal 2p photoabsorption edge. We ascribe the systematic decrease of the magnitude of this effect, going from MnCl 2 to KCl, to the extension of the excited metal 3d wavefunction and, as a consequence, decrease of the overlap between the 3d and 2p atomic orbitals.

Resonant photoemission of CoCl2

Abstract We present the results of a study of the resonant photoemission from polycrystalline in situ evaporated thin film of CoCl2 excited at 2p photoabsorption edges of Co and Cl. At the Co 2p→3d resonance strong enhancement was observed for the Co 3p, valence band photoemission and for spectral regions of L23M23M23, L23M23M45 and L23M45M45 Auger transitions. The results of valence band resonant photoemission is discussed in terms of the available calculations. The valence band resonant spectra exhibit no enhancement in connection to the Cl 2p edge which shows that the Cl 2p absorption pre-edge structure is formed by d- and s-like final delocalized states.

NaK photoabsorption and resonant KLL Auger spectra in naf and NaCl

The nature of Na Is photoabsorption in NaF and NaCl is investigated using the resonant Auger decay of Na Is core excitations. The appearance of new peaks in Auger spectra, when the energy of excitation coincides with the photoabsorption thresholds, shows that the core excitons are created in the threshold region of the Na 1s photoabsorption spectrum. The core excitons around 1074.2 eV originate from the dipole-forbidden 1s(-1)3s final state, the population of which is made possible by the symmetry disruption at the photoabsorption site. Another core exciton, excited at photon energies of 1076.8 eV in NaF and 1076.3 eV in NaCl, originates from 1s(-1)3p states similar to atoms of Ne and Na. Resonant Auger spectra show also that in NaCl the first sharp photoabsorption maximum at 1076.6 eV has only partially excitonic character.