Ag29 nanoclusters capped
with lipoic acid (LA) can be doped with Au. The doped clusters show
enhanced stability and increased luminescence efficiency. We attribute
the higher quantum yield to an increase in the rate of radiative decay.
With mass spectrometry, the Au-doped clusters were found to consist
predominantly of Au1Ag28(LA)123–. The clusters were characterized using X-ray absorption
spectroscopy at the Au L3-edge. Both the extended absorption
fine structure (EXAFS) and the near edge structure (XANES) in combination
with electronic structure calculations confirm that the Au dopant
is preferentially located in the center of the cluster. A useful XANES
spectrum can be recorded for lower concentrations, or in shorter time,
than the more commonly used EXAFS. This makes XANES a valuable tool
for structural characterization.
The VIolation of Pauli exclusion principle -2 experiment, or VIP-2 experiment, at the Laboratori Nazionali del Gran Sasso searches for X-rays from copper atomic transitions that are prohibited by the Pauli exclusion principle. Candidate direct violation events come from the transition of a 2p electron to the ground state that is already occupied by two electrons. From the first data taking campaign in 2016 of VIP-2 experiment, we determined a best upper limit of for the probability that such a violation exists. Significant improvement in the control of the experimental systematics was also achieved, although not explicitly reflected in the improved upper limit. By introducing a simultaneous spectral fit of the signal and background data in the analysis, we succeeded in taking into account systematic errors that could not be evaluated previously in this type of measurements.
Magnetite is one of the most fascinating materials exhibiting the enigmatic first-order Verwey transition which is conventionally manipulated through chemical doping. Here, we show that heating magnetite results in a spontaneous charge reordering and, consequently, a hole self-doping effect at the octahedral sublattice. Core-level x-ray spectroscopy measurements combined with theory uncovers that there are three regimes of self-doping that map the temperature dependence of the electrical conductivity and magnetism up to the Curie temperature. Our results provide an elegant analogy between the effect of chemical doping and temperature-driven self-doping on trimerons in magnetite.
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