Spectral sharpening of the Pt L edges by high-resolution x-ray emission

The platinum 2p(3/2), 2p(1/2), and 2s x-ray absorption spectra, recorded by monitoring the fluorescence intensity with eV energy resolution, show a spectral broadening that is significantly less than the 2p and 2s core hole lifetime broadening. The background of such spectral sharpening is discussed. It is shown, experimentally as well as theoretically, that the lifetime broadening of the 2p and 2s core holes is replaced by a new lifetime broadening. It is demonstrated that from the combination of normal x-ray absorption, selective x-ray absorption, and x-ray emission, the individual lifetimes of all participating core states can be determined. The difference between the 5d(5/2) and 5d(3/2) densities of states can be obtained from a combination of the 2p(1/2) and 2p(3/2) x-ray absorption spectra. The present spectra are limited by the experimental resolution. With the prospect of an improved experimental resolution for x-ray excitation and decay, the Pt edge absorption spectra could be obtained with even better resolution, thus providing a high-resolution hard x-ray probe of the empty density of states with important advantages for in-situ and high-pressure studies

Spectral sharpening of the Pt L edges by high-resolution x-ray emission

The platinum 2p(3/2), 2p(1/2), and 2s x-ray absorption spectra, recorded by monitoring the fluorescence intensity with eV energy resolution, show a spectral broadening that is significantly less than the 2p and 2s core hole lifetime broadening. The background of such spectral sharpening is discussed. It is shown, experimentally as well as theoretically, that the lifetime broadening of the 2p and 2s core holes is replaced by a new lifetime broadening. It is demonstrated that from the combination of normal x-ray absorption, selective x-ray absorption, and x-ray emission, the individual lifetimes of all participating core states can be determined. The difference between the 5d(5/2) and 5d(3/2) densities of states can be obtained from a combination of the 2p(1/2) and 2p(3/2) x-ray absorption spectra. The present spectra are limited by the experimental resolution. With the prospect of an improved experimental resolution for x-ray excitation and decay, the Pt edge absorption spectra could be obtained with even better resolution, thus providing a high-resolution hard x-ray probe of the empty density of states with important advantages for in-situ and high-pressure studies

Quadrupole transitions revealed by Borrmann spectroscopy

The Borrmann effect(1,2) - a dramatic increase in transparency to X- ray beams - is observed when X- rays satisfying Bragg's law diffract through a perfect crystal. The minimization of absorption seen in the Borrmann effect has been explained by noting that the electric field of the X- ray beam approaches zero amplitude at the crystal planes, thus avoiding the atoms. Here we show experimentally that under conditions of absorption suppression, the weaker electric quadrupole absorption transitions are effectively enhanced to such a degree that they can dominate the absorption spectrum. This effect can be exploited as an atomic spectroscopy technique; we show that quadrupole transitions give rise to additional structure at the L-1, L-2 and L-3 absorption edges of gadolinium in gadolinium gallium garnet, which mark the onset of excitations from 2s, 2p(1/2) and 2p(3/2) atomic core levels, respectively. Although the Borrmann effect served to underpin the development of the theory of X- ray diffraction(3-6), this is potentially the most important experimental application of the phenomenon since its first observation seven decades ago. Identifying quadrupole features in X- ray absorption spectroscopy is central to the interpretation of 'pre- edge' spectra, which are often taken to be indicators of local symmetry, valence and atomic environment(7). Quadrupolar absorption isolates states of different symmetries to that of the dominant dipole spectrum, and typically reveals orbitals that dominate the electronic ground- state properties of lanthanides and 3d transition metals, including magnetism. Results from our Borrmann spectroscopy technique feed into contemporary discussions regarding resonant X- ray diffraction(8) and the nature of pre-edge lines identified by inelastic X- ray scattering(7). Furthermore, because the Borrmann effect has been observed in photonic materials, it seems likely that the quadrupole enhancement reported here will play an important role in modern optics

Accountability in Nonprofit Sector

Accountability in nonprofit sector concerns an articulated assessment of global and overall consistency inherent in the following key elements: (a) Transparent use of financial and nonfinancial resources. (b) Correctness of management and governance. (c) Adequacy and conformity between actions and objectives. (d) Clear communication of the results achieved. In essence, it is intended to refer to the application of the concept of accountability to the non-profit sector. If the generic term accountability is very multifaceted, as it is highly debated and chameleon-like (Mulgan 2000; Messner 2009), it is even more complex and profound when referring to nonprofit institutions (NPIs) (Rademacher and Remus 2017). In fact, it presents an evident versatility, being able to represent a principle, a duty, a system, a process, a mechanism, a set of tools and techniques (Ricci 2019): it describes the need to report, responsibly, the work of NPIs towards all stakeholders regarding the use of the resources, the correctness of the management, the correspondence and the consistency of the activities with respect to the programmed objectives (Ricci 2016). The final aim is to allow the correct demonstration of social value (Campbell 2002) and public value (Moore 1995; Esposito and Ricci 2015) generated by NPIs, which are necessary to guarantee their success (Krisch and Grabner-Kräuter 2017)