Method for the definitive detection of orbital angular momentum states in neutrons by spin-polarized He.

A standard method to detect thermal neutrons is the nuclear interaction He(n,p)H. The spin dependence of this interaction is also the basis of a neutron spin-polarization filter using nuclear polarized He. We consider the corresponding interaction for neutrons placed in an intrinsic orbital angular momentum (OAM) state.

Resonant X-ray Emission and Valence-band Lifetime Broadening in LiNO.

X-ray absorption and resonant inelastic x-ray scattering measurements are carried out on lithium nitrate LiNO. The nitrogen orbitals exhibit a large lifetime effect. Experimentally, this is manifest as an apparent weakening of the x-ray emission signal from these states, but a closer examination shows that instead it is due to extreme broadening.

Intrinsic Orbital Angular Momentum States of Neutrons.

It has been shown that single-particle wave functions, of both photons and electrons, can be created with a phase vortex, i.e., an intrinsic orbital angular momentum (OAM).

Resonant X-ray Emission of Hexagonal Boron Nitride.

The electronic structure of hexagonal boron nitride (BN) is explored using measurements of x-ray absorption and resonant inelastic x-ray scattering (RIXS) at the nitrogen K edge (1) in tandem with calculations using many-body perturbation theory within the and Bethe-Salpeter equation (BSE) approximations. Our calculations include the effects of lattice disorder from phonons activated thermally and from zero point energy. They highlight the influence of disorder on near-edge x-ray spectra.

Quasiparticle Lifetime Broadening in Resonant X-ray Scattering of NHNO.

It has been previously shown that two effects cause dramatic changes in the x-ray absorption and emission spectra from the N K edge of the insulating crystal ammonium nitrate. First, vibrational disorder causes major changes in the absorption spectrum, originating not only from the thermal population of phonons, but, significantly, from zero-point motion as well. Second, the anomalously large broadening ( 4 eV) of the emission originating from nitrate states is due to unusually short lifetimes of quasiparticles in an otherwise extremely narrow band.

Surface effects on the crystallization of cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) and the consequences for its N K X-ray emission spectrum.

Recent studies of the crystallization of cyclotrimethylene-trinitramine (RDX) have shown that the presence of the α- and β-phases of the compound is sensitive to the substrate when using drop cast crystallization methods. The specific phase has potential consequences for measurements of the nitrogen K X-ray emission spectrum (XES) that were recently reported for this compound using samples crystallized on In metal substrates. We have determined that the crystallization of RDX on a clean In metal substrate starts out completely as the β-phase but progressively incorporates the α-phase as the film thickens.

X-ray emission spectroscopy of nitrogen-rich compounds.

Nonresonant X-ray emission spectroscopy was used to compare the nitrogen-rich compounds ammonium nitrate, trinitrotoluene, and cyclotrimethylene-trinitramine. They are representative of crystalline and molecular structures of special importance in industrial and military applications. The spectral signature of each substance was analyzed and correlated with features in the electronic structure of the systems.

Variable Magnification With Kirkpatrick-Baez Optics for Synchrotron X-Ray Microscopy.

We describe the distinction between the operation of a short focal length x-ray microscope forming a real image with a laboratory source (convergent illumination) and with a highly collimated intense beam from a synchrotron light source (Köhler illumination). We demonstrate the distinction with a Kirkpatrick-Baez microscope consisting of short focal length multilayer mirrors operating at an energy of 8 keV. In addition to realizing improvements in the resolution of the optics, the synchrotron radiation microscope is not limited to the usual single magnification at a fixed image plane.