An ultraviolet photoelectron spectroscopic study of BF3–donor complexes

He i spectra of strong n–v type adducts of BF3 with H2O, CH3OH, (C2H5)2O, and CH3CN as well as of weak complexes of BF3 with NO and H2S are reported along with assignments based on MO calculations. The energy of the fluorine orbitals of BF3 is shown to be shifted in proportion to the strength of the donor–acceptor interaction. BF3 seems to form a contact pair with CS2.

Electronic structure of high-Tc Ba0.6K0.4BiO3 by x-ray photoelectron spectroscopy

We have investigated the electronic structure of Ba1-xKxBiO3 (0photoelectron spectroscopy. The Bi(4f) core levels show a normal valency of +3 as in Bi2O3 and we find no evidence for the disproportionation of Bi4+ to Bi3+ and Bi5+. Instead, we find that BaBiO3 has mixed valent O2- and O1- ions. As the potassium doping is increased, the binding energy of the O2- ions in the O(1s) photoelectron spectra steadily decreases from 529.7 to 528.8 eV. The effect of lowering the O(1s) binding energy is to raise the O(2p) band towards EF and at the superconducting composition a finite density of O(2p) states is observed near EF. Similarly, the Ba(5p) binding energies decrease with potassium doping, indicating increased metallicity. The behavior of the O(1s), Ba(5p), and the valence band resembles that of all the cuprate superconductors and we conclude that in all these oxide superconductors, a hole in the (filled) O(2p) band is the carrier responsible for superconductivity, which predicts hole conduction in the Ba-K-Bi-O and Ba-Pb-Bi-O systems.

Design and fabrication of an indigenous molecular beam ultraviolet photoelectron spectrometer

An ultraviolet photoelectron spectrometer for the study of van der Waals molecules has been designed and fabricated indigenously. The spectrometer consists of an HeI discharge lamp, a molecular beam sample inlet system, an electrostatic lens, a 180-degrees hemispherical electrostatic analyser and a channeltron detector. Performance of the spectrometer is illustrated with an example.

Transition metal oxide perovskites by photoelectron and x-ray absorption spectroscopy

X-ray and ultraviolet photoelectron spectroscopy as well as x-ray absorption spectroscopy have been employed to investigate transition metal oxide perovskites of the general formula ABOs (A=La or rare-earth ion, B=trivalent transition metalion). Systematics in the core levels and in the valence bands in the series of LaBOa compounds have been discussed. Lanthanum chemical shifts in the x-ray absorption spectra in this series show interesting trends. Photoelectron spectra of the solid solutions, LaNil_x Coxes, LaNix_x FexO8 and LaFel_x Coxes show that the rigid band model is applicable to these systems. It is shown that x-ray photoelectron spectroscopy can be employed to identify multiple oxidation states of transition metal ions in oxide perovskites.

Systematic Organic UV Photoelectron Spectroscopy

Photoelectron spectroscopy (PES) provides valuable information on the ionization energies of atoms and molecules. The ionization energy (IE) is given by the relation.hv = IE + T where hv is t h e energy of the radiation and T i s the kinetic energy of the electron. The IEs are directly related to the orbital energies (Koopmans' theorem). By employing UV radiation (HeI. 21.2 eV. or HeII. 40.8 eV). extensive data on the ionization of valence electrons in organic molecules have been obtained in recent years. These studies of UV photoelectron spectroscopy. originated by Turner, have provided a direct probe into the energy levels of organic molecules. Molecular orbital calculations of various degrees of sophistication are generally employed to make assignments of the PES bands. Analysis of the vibrational structure of PES bands has not only provided structural information on the molecular ions, but has also been of value in band assignments. Dewar and co-workers [1, 2) presented summaries of available PES data on organic molecules in 1969 and 1970. Turner et al. [3] published a handbook of Hel spectra of organic molecules in 1970. Since then, a few books [4-7] discussing the principles and applications of UV photoelectron spectroscopy have appeared of which special mention should be made of the recent article by Heilbronner and Maier [7]. There has, however, been no comprehensive review of the vast amount of data on the UV-PES of organic molecules published in the literature since 1970.

Metal-insulator transitions in Cr-doped V2O3 by x-ray and ultraviolet photoelectron spectroscopy

X-ray and ultraviolet photoelectron spectroscopy have been employed to investigate the high temperature metal-insulator transitions in V2O3 and (V0.99Cr0.01)2O3. The high temperature transitions are associated with more gradual changes in the 3d bands compared to the low-temperature transitions

A Photoelectron Spectroscopic Study Of The Interaction Of Oxygen, Nitrogen And Transition-Metals With C-60 Films

Evidence is presented for the strong interaction of oxygen and nitrogen with solid films of buckminsterfullerene based on core-level spectroscopic studies. Cr, Ni and Cu deposited on C60 films interact strongly giving rise to large changes in the C(Is) and C(2p) binding energies as well as the (2p) binding energies of the transition metals.

An investigation of well-characterized small gold clusters by photoelectron spectroscopy, tunneling spectroscopy, and cognate techniques

After microscopic characterization of the size distributions of gold clusters, deposited on carbon substrates by vacuum evaporation or by soft landing, Au(4f') binding energy of the clusters has been measured as a function of the mean cluster size. Similar measurements have been carried out on Au clusters prepared from sols by chemical means and high-nuclearity cluster compounds. In general, small clusters with a mean diameter of $2 nm show significantly larger binding energies than the bulk metal value, due to the onset of nonmetallicity. Nonmetallicity manifests itself in terms of a tunneling conductance gap only in clusters of diameter ;5 1 nm containing 40 atoms or fewer.