Electron paramagnetic resonance and photochromism of N3V0\mathrm{N}_{3}\mathrm{V}^{0} in diamond

The defect in diamond formed by a vacancy surrounded by three nearest-neighbor nitrogen atoms and one carbon atom, $\mathrm{N}_{3}\mathrm{V}$, is found in $\approx98\%$ of natural diamonds. Despite $\mathrm{N}_{3}\mathrm{V}^{0}$ being the earliest electron paramagnetic resonance spectrum observed in diamond, to date no satisfactory simulation of the spectrum for an arbitrary magnetic field direction has been produced due to its complexity. In this work, $\mathrm{N}_{3}\mathrm{V}^{0}$ is identified in $^{15}\mathrm{N}$-doped synthetic diamond following irradiation and annealing. The $\mathrm{^{15}N}_{3}\mathrm{V}^{0}$ spin Hamiltonian parameters are revised and used to refine the parameters for $\mathrm{^{14}N}_{3}\mathrm{V}^{0}$, enabling the latter to be accurately simulated and fitted for an arbitrary magnetic field direction. Study of $\mathrm{^{15}N}_{3}\mathrm{V}^{0}$ under excitation with green light indicates charge transfer between $\mathrm{N}_{3}\mathrm{V}$ and $\mathrm{N_s}$. It is argued that this charge transfer is facilitated by direct ionization of $\mathrm{N}_{3}\mathrm{V}^{-}$, an as-yet unobserved charge state of $\mathrm{N}_{3}\mathrm{V}$

Surveying the solar system by measuring angles and times: from the solar density to the gravitational constant

A surprisingly large amount of information on our solar system can be gained from simple measurements of the apparent angular diameters of the sun and the moon. This information includes the average density of the sun, the distance between earth and moon, the radius of the moon, and the gravitational constant. In this note it is described how these and other quantities can be obtained by simple earthbound measurements of angles and times only, without using any explicit information on distances between celestial bodies. The pedagogical and historical aspects of these results are also discussed briefly.Comment: 12 pges, one figur

Dilute Bose gases interacting via power-law potentials

Neutral atoms interact through a van der Waals potential which asymptotically falls off as r^{-6}. In ultracold gases, this interaction can be described to a good approximation by the atom-atom scattering length. However, corrections arise that depend on the characteristic length of the van der Waals potential. We parameterize these corrections by analyzing the energies of two- and few-atom systems under external harmonic confinement, obtained by numerically and analytically solving the Schrodinger equation. We generalize our results to particles interacting through a longer-ranged potential which asymptotically falls off as r^{-4}.Comment: 7 pages, 4 figure

Orbiting passive microwave sensor simulation applied to soil moisture estimation

A sensor/scene simulation program was developed and used to determine the effects of scene heterogeneity, resolution, frequency, look angle, and surface and temperature relations on the performance of a spaceborne passive microwave system designed to estimate soil water information. The ground scene is based on classified LANDSAT images which provide realistic ground classes, as well as geometries. It was determined that the average sensitivity of antenna temperature to soil moisture improves as the antenna footprint size increased. Also, the precision (or variability) of the sensitivity changes as a function of resolution

Generalized L\"uscher Formula in Multi-channel Baryon-Meson Scattering

L\"uscher's formula relates the elastic scattering phase shifts to the two-particle energy levels in a finite cubic box. The original formula was obtained for elastic scattering of two massive spinless particles in the center of mass frame. In this paper, we consider the case for the scattering of a spin 1/2 particle with a spinless particle in multi-channel scattering. A generalized relation between the energy of two particle system and the scattering matrix elements is established. We first obtain this relation using quantum-mechanics in both center-of-mass frame and in a general moving frame. The result is then generalized to quantum field theory using methods outlined in Ref. \cite{Hansen:2012tf}. We verify that the results obtained using both methods are equivalent up to terms that are exponentially suppressed in the box size.Comment: One reference adde

Explosive events associated with a surge

The solar atmosphere contains a wide variety of small-scale transient features. Here, we explore the inter-relation between some of them such as surges, explosive events and blinkers via simultaneous spectral and imaging data taken with the TRACE imager, the SUMER, and CDS spectrometers on board SoHO, and SVST La Palma. The alignment of all data both in time and solar XY shows that SUMER line profiles, which are attributed to explosive events, are due to a surge phenomenon. The surge is triggered, most probably, by one or more Elerman bombs which are best visible in Halpha +-350 A but were also registered by TRACE Fe IX/X 171 A and correspond to a strong radiance increase in the CDS Mg IX 368.07 A line. With the present study we demonstrate that the division of small-scale transient events into a number of different subgroups, for instance explosive events, blinkers, spicules, surges or just brightenings, is ambiguous, implying that the definition of a feature based only on either spectroscopic or imaging characteristics as well as insufficient spectral and spatial resolution can be incomplete.Comment: 17 pages, 7 figures, 1 tabl

The neutral silicon-vacancy center in diamond: spin polarization and lifetimes

We demonstrate optical spin polarization of the neutrally-charged silicon-vacancy defect in diamond ($\mathrm{SiV^{0}}$), an $S=1$ defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but non-zero at below-resonant energies. We measure an ensemble spin coherence time $T_2>100~\mathrm{\mu s}$ at low-temperature, and a spin relaxation limit of $T_1>25~\mathrm{s}$. Optical spin state initialization around 946 nm allows independent initialization of $\mathrm{SiV^{0}}$ and $\mathrm{NV^{-}}$ within the same optically-addressed volume, and $\mathrm{SiV^{0}}$ emits within the telecoms downconversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that $\mathrm{SiV^{0}}$ is a promising candidate for a long-range quantum communication technology

Antibound States and Halo Formation in the Gamow Shell Model

The open quantum system formulation of the nuclear shell model, the so-called Gamow Shell Model (GSM), is a multi-configurational SM that employs a single-particle basis given by the Berggren ensemble consisting of Gamow states and the non-resonant continuum of scattering states. The GSM is of particular importance for weakly bound/unbound nuclear states where both many-body correlations and the coupling to decay channels are essential. In this context, we investigate the role of l=0 antibound (virtual) neutron single-particle states in the shell model description of loosely bound wave functions, such as the ground state wave function of a halo nucleus 11Li