NEXAFS multiple scattering calculations of KO_2

Since many years the oxidation of alkali metals has being attracted much interest due to the catalytic properties of metal promoters and the simple electronic structure of alkali atoms. The alkali-oxides phase diagram indicates that the interaction of oxygen with alkali metals can lead to the formation of different atomic O2- ions and molecular O_2 and O^(2-) ions. Potassium superoxide has been prepared in situ and high resolution O k-edge absorption NEXAFS spectra have been measured at the VUV beam-line at ELETTRA facility. The experimental data have been analyzed by multiple scattering approach deriving many geometrical and electronic details. In particular, we have found that the growth material structure is of the KO_2 type with an O-O distance of about 1.35 Angstrom and that the transition involving single pi molecular empty state of the superoxide O_2^(2-) anion has a fine structure. Multiple Scattering self consistent calculation indicates that the bond between oxygen anion and K atom is totally ionic and that the fine structure is essentially due to solid state effects

NEXAFS experiment and multiple scattering calculations on KO_2: effects on the π resonance in the solid phase

The high-energy resolution O K-edge absorption near-edge x-ray absorption fine structure spectrum has been measured for in situ prepared potassium superoxide. The experimental data have been analyzed in detail by multiple scattering calculations using self-consistent field potentials. In particular, the so-called π resonance at the rising edge, which presents a double-peak structure, has been totally resolved and reproduced by the calculations. This analysis indicates that the grown material is arranged in a KO_2 structure with an O-O distance between 1.31 and 1.34 Angstrom. Moreover, the calculation demonstrates both a complete ionic character of the bound between the Oˆ(2-) anion and K atoms and a strong interaction between the anion and solid-state matrices

On the electronic properties of the quasi-one-dimensional crystal Nb4Te17I4

We studied the newly synthesized quasi-one-dimensional compound Nb4Te17I4. Resistivity measurements confirmed its pseudo-one-dimensional character and photoemission spectroscopy clarified the nature of its valence band states. This polytelluride is a narrow-gap semiconductor at room temperature, with a forbidden gap width of 0.34 eV

Observation of Ar(2p(5)3p(5)nln'l') and Ne(1s2p(5)nln'l') inner-shell doubly excited states RID G-7348-2011

The photoabsorption spectra of neon and argon in the energy region of the 1s2p(5)nln'l' and 2p(5)3p(5)nln'l' doubly excited states have been studied. The resolution and flux of the new VUV undulator beam line at ELETTRA allowed the resolution of new features for Ne and the first observation for Ar. A comparison of the measured photoabsorption spectra and of the threshold photoelectron spectra in the energy region of the Ne+ 1s2p(5)nl and Ar+ 2p(5)3p(5)nl satellite states provides information on the decay routes of the inner-shell doubly excited states

Interference effects in the Auger decay of the resonantly excited 2p(3/2)(-1)3d state of argon RID G-7348-2011

High resolution resonant Auger spectra have been measured at the VUV beam line at ELETTRA, Sincrotrone Trieste, while tuning the photon energy across the 2p(3/2)(-1)3d resonance of argon. A large variation of the branching ratio for decay into the spectator 3p(-2)3d and shakeup 3p(-2)4d channels is observed. The effect has not been seen previously in resonant inner-shell excitation and is attributed to the interference between the direct photoionization process and resonant Auger decay leading to the same final state

C59N Monomers: Stabilisation through immobilisation.

C59N is found to sublime in monomer free radical form rather than the more stable dimers which are normally observed. Using a scanning tunneling microscope operating in ultrahigh vacuum we have found that the monomer form may be immobilized and therefore stabilized on clean Si surfaces. On the less reactive H-terminated Si(100) surface C59N diffuses and forms disordered islands, and a lower limit for the interaction energy between two monomers may be estimated at 0.8 eV. Synchrotron based photoemission experiments have also been performed and show diffusion and redimerization occur for multilayer deposition of C59N