arXiv subjects

G. Stefani

Publications and source records attributed to G. Stefani.

4 recordsLinked to original sources

arXiv2022

A distributional approach to fractional Sobolev spaces and fractional variation: asymptotics I

We continue the study of the space $BV^α(\mathbb{R}^n)$ of functions with bounded fractional variation in $\mathbb{R}^n$ of order $α\in(0,1)$ introduced in arXiv:1809.08575, by dealing with the asymptotic behaviour of the fractional operators involved. After some technical improvements of certain results of our previous work, we prove that the fractional $α$-variation converges to the standard De Giorgi's variation both pointwise and in the $Γ$-limit sense as $α\to1^-$. We also prove that the fractional $β$-variation converges to the fractional $α$-variation both pointwise and in the $Γ$-limit sense as $β\toα^-$ for any given $α\in(0,1)$.

math.FA↗

arXiv2020

Unexpectedly large electron correlation measured in Auger spectra of ferromagnetic iron thin films: orbital-selected Coulomb and exchange contributions

A set of electron-correlation energies as large as 10 eV have been measured for a magnetic 2ML Fefilm deposited on Ag(001). By exploiting the spin selectivity in angle-resolved Auger-photoelectroncoincidence spectroscopy and the Cini-Sawatzky theory, the core-valence-valence Auger spectrumof a spin-polarized system have been resolved: correlation energies have been determined for eachindividual combination of the two holes created in the four sub-bands involved in the decay: majorityand minority spin, as well asegandt2g. The energy difference between final states with paralleland antiparallel spin of the two emitted electrons is ascribed to the spin-flip energy for the final ionstate, thus disentangling the contributions of Coulomb and exchange interactions.

cond-mat.str-el↗

arXiv2019

Space-Charge effect in electron time-of-flight analyzer for high-energy photoemission spectroscopy

The space-charge effect, due to the instantaneous emission of many electrons after the absorption of a single photons pulse, causes distortion in the photoelectron energy spectrum. Two calculation methods have been applied to simulate the expansion during a free flight of clouds of mono- and bi-energetic electrons generated by a high energy pulse of light and their results have been compared. The accuracy of a widely used tool, such as SIMION(R), in predicting the energy distortion caused by the space-charge has been tested and the reliability of its results is verified. Finally we used SIMION(R) to take into account the space-charge effects in the simulation of simple photoemission experiments with a time-of-flight analyzer.

physics.ins-det↗

arXiv2003

Relevance of the EEL spectroscopy for in-situ studies of the growth mechanism of copper-phthalocyanine molecules on metal surfaces: Al(100)

Reflection electron energy loss spectroscopy (EELS) in specular and off specular geometry has been employed to study the early stage of the copper phthalocyanine (CuPc) growth on Al (100) substrate. EEL spectroscopy has been a useful tool in order to study electronic structure of molecular films also in the submonolayer regime. The electronic structure of the first deposited layer of CuPc is strongly influenced by charge transfer from the Al substrate to the lowest unoccupied molecular orbital (LUMO). The strong molecule-substrate interaction gives rise to a coverage dependent frequency shift of the Al surface plasmon. Successive layers have essentially the electronic structure of the molecular solid. Momentum resolved EELS measurements reveal that, in the case of the thicker film investigated (22 Å), the plane of the molecule is almost perpendicular to the surface of the substrate.

cond-mat.mtrl-sci↗