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Defect centers in hexagonal boron nitride represent room-temperature single-photon sources in a layered van der Waals material. These light emitters appear with a wide range of transition energies ranging over the entire visible spectrum,…
We present an ab initio description of optical and shallow-core x-ray absorption spectroscopies in a unified formalism based on the pseudopotential plane-wave method at the level of the Bethe-Salpeter equation (BSE) within Green's functions…
The scattering amplitude from a set of discrete states coupled to a continuum became known as the Fano profile, characteristic for its asymmetric lineshape and originally investigated in the context of photoionization. The generality of the…
We present a deep ASCA observation of a Broad Absorption Line Quasar (BALQSO) PG0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra…
A theoretical description of local absorption is proposed in order to investigate spectral variations on a length scale comparable with the extension of the relevant quantum states. A general formulation is derived within the density-matrix…
In this article, the hydrogen column densities derived from X-ray observations of type II (hidden) quasars and broad absorption line quasars (BALQSOs) are compared. These column densities represent the amount of absorbing material between…
Spectroscopy has played the key role in revealing, and thereby understanding, the structure of atoms and molecules. A central drive in this field is the pursuit of higher precision and accuracy so that ever more subtle effects might be…
As one of the most luminous radio-loud quasars showing intrinsic ultraviolet (UV) and X-ray absorption, 3C 351 provides a laboratory for studying the kinematics and physical conditions of such ionized absorbers. We present an analysis of…
Activation of shallow acceptor state has been observed in ion irradiated and subsequently air annealed polycrystalline ZnO material. Low temperature photoluminescence (PL) spectrum of the sample exhibits clear signature of acceptor bound…
There exists a significant population of broad line, z~2 QSOs which have heavily absorbed X-ray spectra. Follow up observations in the submillimetre show that these QSOs are embedded in ultraluminous starburst galaxies, unlike most…
Ionizing sources embedded in the neutral intergalactic medium (IGM) before cosmological reionization generate discrete HII regions. We show that a sufficiently bright quasar (for example, one tenth as luminous as that recently discovered by…
Broad Absorption Line Quasars (BALQs) are actively accreting supermassive black holes that have strong outflows characterized by broad absorption lines in their rest-UV spectra. Variability in these absorption lines occurs over months to…
A new generation of sensitive X-ray measurements are indicating that the existence of X-ray attenuation column densities, $N_{H}>10^{24}\mathrm{cm}^{-2}$ is quite common amongst broad absorption line quasars (BALQSOs). This is significant…
Until now, the spectral changes observed from persistent to dipping intervals in dipping low-mass X-ray binaries were explained by invoking progressive and partial covering of an extended emission region. Here, we propose a novel and…
Weyl semimetals are 3D phases of matter with topologically protected states that have remarkable macroscopic transport behaviors. As phonon dynamics and electron-phonon scattering play a critical role in the electrical and thermal…
We present the results of EVN+MERLIN VLBI polarization observations of 8 Broad Absorption Line (BAL) quasars at 1.6 GHz, including 4 LoBALs and 4 HiBALs with either steep or flat spectra on VLA scales. Only one steep-spectrum source,…
An approach is presented for the atomistic study of phonon transport in real dielectric nanowires via Green functions. The formalism is applied to investigate the phonon flow through nanowires coated by an amorphous material. Examples for a…
Collinear laser spectroscopy has been performed on He-like C$^{4+}$ ions extracted from an electron beam ion source (EBIS). In order to determine the transition frequency with the highest-possible accuracy, the lineshape of the fluorescence…
We present a first detailed spectrum synthesis calculation of a supernova-fallback disk composed of iron. We assume a geometrically thin disk with a radial structure described by the classical alpha-disk model. The disk is represented by…
We present the hard X-ray (20-100 keV) observations of Cygnus X-1 obtained using a large area balloon-borne Xenon filled Multi-anode Proportional Counter (XMPC) telescope. The observations were carried out during the gamma_2 state of the…