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Written by leading experts in the field, the first edition of this textbook was the first of its kind to address numerous potential applications such as the technology of high-voltage insulation in pulsed inhomogeneous fields, and applications related to cavitation development in liquid dielectrics, treatment of different materials and plasma medicine. This new expanded edition also addresses the development of the theory over the past few years and features extensive revisions and some expanded chapters. It is intended for a broad audience, from students to engineers and scientists, who are interested in current research questions in electrodynamics and hydrodynamics of liquid dielectrics. Part of IOP Series in Plasma Physics.

All students of physics encounter the Bohr model of the atom. However, it is often covered quickly in order that curricula can progress to wave mechanics. This book gives students and instructors a fuller exploration to Bohr's model. Topics covered include the historical background to the model, Bohr's approach to his original derivation, and corollary issues such as the role of angular momentum in the theory, ionized helium, the correspondence principle, the fine-structure constant, de Broglie matter-waves, application of the theory to the diatomic hydrogen molecule, and the magnetic field created by the orbiting electron. It also includes student exercises, a bibliography, a list of important physical constants, and a survey of Bohr's subsequent life and career.

The response of cryogenic high-resolution detectors to a short-pulse laser consists of a Poisson-distributed set of equidistant peaks that correspond to integer numbers of absorbed photons. Since the laser has a negligible intrinsic line width, the peaks can be used for detailed characterization of both the detector and the data acquisition system. We have characterized our superconducting tunnel junction (STJ) photon detectors in the UV and soft X-ray range with a pulsed 355-nm laser at rates up to 5000 counts/s. The observed peaks are described by a Gaussian to very high accuracy, with a width between ~ 1 and ~ 3 eV FWHM depending on the detector area and the absorbed energy. For high statistics, centroids can be determined with a precision of order 1 meV over an energy range of several 100 eV. This allows identifying and correcting for non-linearities in the digitizer that can otherwise limit the calibration accuracy.

The generation of attosecond pulse trains at free-electron lasers opens new opportunities in ultrafast science, as it gives access, for the first time, to reproducible, programmable, extreme ultraviolet (XUV) waveforms with high intensity. In this work, we present a detailed analysis of the theoretical model underlying the temporal characterization of the attosecond pulse trains recently generated at the free-electron laser FERMI. In particular, the validity of the approximations used for the correlated analysis of the photoelectron spectra generated in the two-color photoionization experiments are thoroughly discussed. The ranges of validity of the assumptions, in connection with the main experimental parameters, are derived.

For many years we have known that dust in the form of a dusty-molecular torus is responsible for the obscuration in active galactic nuclei (AGN) at large viewing angles and, thus, for the widely used phenomenological classification of AGN. Recently, we gained new observational and theoretical insights into the geometry of the torus region and the role of dust in the dynamics of emerging outflows and failed winds. We will briefly touch on all these aspects and provide a more detailed update of our dust-based model (FRADO—Failed Radiatively Accelerated Dusty Outflow) capable of explaining the processes of formation of Balmer lines in AGN. Graphic abstract

This study is an overview of the atomic data and opacity computations performed by the Atomic Physics and Astrophysics Unit of Mons University in the context of kilonova emission following neutron star mergers, in both the photospheric and nebular phases. In this work, as a sample case, we focus on a specific lanthanide ion, namely Er III. As far as the LTE photospheric phase of the kilonova ejecta is concerned, we present our calculations using both a theoretical method (the pseudo-relativistic Hartree-Fock method, HFR) and a statistical approach (the Resolved Transition Array approach, RTA) to obtain the atomic data required to estimate the Er III expansion opacity for typical conditions expected in kilonova ejecta one day after the merger. In order to draw the limitations of both of our strategies, the results obtained using the latter are compared, and a calibration procedure of the HFR atomic data in this context is also discussed. Concerning the kilonova ejecta nebular phase, atomic parameters that characterize forbidden lines in Er III are calculated using HFR as well as another computational approach, namely the Multiconfiguration Dirac–Hartree–Fock (MCDHF) method. The potential detection of such lines in late-phase kilonova spectra is then discussed. Graphical abstract

The theoretical framework of energy-density functionals has been used to show that the depth of the confining nuclear potential has an important role in cluster formation, with a pronounced effect for relativistic functionals. Clustering behaviour of nucleons Nucleonic matter — the protons and neutrons that comprise atomic nuclei — acts predominantly as a quantum liquid, but lighter nuclei behave more like molecules composed of clusters of protons and neutrons. Clustering is related to the overall nuclear interaction, but its detailed mechanism is not fully understood. These authors use theoretical modelling to calculate the conditions that cause clustering in neon-20, a small nucleus thought to favour clustering. They find that the depth of the confining nuclear potential plays an important part in cluster formation, with a particularly pronounced effect for relativistic functionals. More generally, clustering is considered as a transitional phenomenon between crystalline and quantum liquid phases. Nucleonic matter displays a quantum-liquid structure, but in some cases finite nuclei behave like molecules composed of clusters of protons and neutrons. Clustering is a recurrent feature in light nuclei, from beryllium to nickel 1 , 2 , 3 . Cluster structures are typically observed as excited states close to the corresponding decay threshold; the origin of this phenomenon lies in the effective nuclear interaction, but the detailed mechanism of clustering in nuclei has not yet been fully understood. Here we use the theoretical framework of energy-density functionals 4 , 5 , encompassing both cluster and quantum liquid-drop aspects of nuclei, to show that conditions for cluster formation can in part be traced back to the depth of the confining nuclear potential. For the illustrative example of neon-20, we show that the depth of the potential determines the energy spacings between single-nucleon orbitals in deformed nuclei, the localization of the corresponding wavefunctions and, therefore, the degree of nucleonic density clustering. Relativistic functionals, in particular, are characterized by deep single-nucleon potentials. When compared to non-relativistic functionals that yield similar ground-state properties (binding energy, deformation, radii), they predict the occurrence of much more pronounced cluster structures. More generally, clustering is considered as a transitional phenomenon between crystalline and quantum-liquid phases of fermionic systems.

Transition metal ions provide a rich set of optically active defect spins in wide bandgap semiconductors. Chromium (Cr4+) in silicon-carbide (SiC) produces a spin-1 ground state with a narrow, spectrally isolated, spin-selective, near-telecom optical interface. However, previous studies were hindered by material quality resulting in limited coherent control. In this work, we implant Cr into commercial 4H-SiC and show optimal defect activation after annealing above 1600 °C. We measure an ensemble optical hole linewidth of 31 MHz, an order of magnitude improvement compared to as-grown samples. An in-depth exploration of optical and spin dynamics reveals efficient spin polarization, coherent control, and readout with high fidelity (79%). We report T1 times greater than 1 s at cryogenic temperatures (15 K) with a T2* = 317 ns and a T2 = 81 μs, where spin dephasing times are currently limited by spin–spin interactions within the defect ensemble. Our results demonstrate the potential of Cr4+ in SiC as an extrinsic, optically active spin qubit.

The atomic electron orbitals that underlie molecular bonding originate from the central Coulomb potential of the atomic core. We used scanning tunneling microscopy and density functional theory to explore the relation between the nearly spherical shape and unoccupied electronic structure of buckminsterfullerene (C60) molecules adsorbed on copper surfaces. Besides the known pi* antibonding molecular orbitals of the carbon-atom framework, above 3.5 electron volts we found atomlike orbitals bound to the core of the hollow C60 cage. These \"superatom\" states hybridize like the s and p orbitals of hydrogen and alkali atoms into diatomic molecule-like dimers and free-electron bands of one-dimensional wires and two-dimensional quantum wells in C60 aggregates. We attribute the superatom states to the central potential binding an electron to its screening charge, a property expected for hollow-shell molecules derived from layered materials.

The beryllium dimer is a deceptively simple molecule that, in spite of having only eight electrons, poses difficult challenges for ab initio quantum chemical methods. More than 100 theoretical investigations of the beryllium dimer have been published, reporting a wide range of bond lengths and dissociation energies. In contrast, there have been only a handful of experimental studies that provide data against which these models could be tested. Ultimately, the uncertain extrapolation behavior associated with the available data has prevented quantitative comparisons with theory. In our experiment, we resolve this issue by recording and analyzing spectra that sample all the bound vibrational levels of the beryllium dimer molecule's electronic ground state. After more than 70 years of research on this problem, the experimental data and theoretical models for the dimer are finally reconciled.