相关论文: Scattering of X-ray emission lines by a helium ato…

In many astrophysical objects an account for scattering of the X-ray fluorescent and resonance lines of iron ions by the electrons, bound in atomic and molecular hydrogen is important. Specific distortions of the scattered line profile…

A scanning helium microscope typically utilises a thermal energy helium atom beam, with an energy and wavelength (<100 meV, ~0.05 nm) particularly sensitive to surface structure. An angular detector stage for a scanning helium microscope is…

Scattering and absorption of X-rays by interstellar dust is calculated for a model consisting of carbonaceous grains and amorphous silicate grains. The calculations employ realistic dielectric functions with structure near X-ray absorption…

For the purpose of deriving the helium abundances in chemically peculiar stars, the importance of assuming a correct helium abundance has been investigated for determining the effective temperature and gravity of main sequence B-type stars,…

We have investigated the formation of helium droplets in two physical situations. In the first one, droplets are atomised from superfluid or normal liquid by a fast helium vapour flow. In the second, droplets of normal liquid are formed…

In previous papers we have proposed a method for the ab initio calculation of fully differential cross-sections for electron scattering in liquids and applied it to liquid argon, xenon and krypton. In this paper, we extend the procedure to…

Theory predicts that a plane wave scattered by a thin slab of gas yields, in the forward direction and under specific circumstances, a larger irradiance than would be observed in the absence of the gas. This enhanced Rayleigh scattering…

Helium nanodroplets are ideal model systems to unravel the complex interaction of condensed matter with ionizing radiation. Here we study the effect of purely elastic electron scattering on angular and energy distributions of photoelectrons…

High resolution X-ray imaging offers a unique opportunity to probe the nature of dust in the z ~< 2 universe. Dust grains 0.1- 1 um in size will scatter soft X-rays, producing a diffuse "halo" image around an X-ray point source, with a…

We show that element diffusion can produce large fluctuations in the initial helium abundance of the star-forming clouds. Diffusion time-scale, which in stars is much larger than the Hubble time, can fall below 10^8 years in the neutral gas…

We demonstrate the abilities of elastic x-ray scattering to yield information on dense matter with multiple ion species and on the microscopic mixing in dense materials. Based on partial structure factors from ab initio simulations, a novel…

Iglesias et al. (2002) showed that the Rayleigh scattering from helium atoms decreases by collective effects in the atmospheres of cool white dwarf stars. Their study is here extended to consider an accurate evaluation of the atomic…

There are observational facts and theoretical arguments for an origin of gamma-ray bursts in molecular clouds in distant galaxies. If this is true, one could detect a significant flux of GRB prompt and early afterglow X-ray radiation…

Neutron Compton scattering measurements have the potential to provide direct information about atomic momentum distributions and adiabatic energy surfaces in condensed matter. First applied to measuring the condensate fraction in superfluid…

Rayleigh scattering is a result of an interaction of photons with bound electrons. Rayleigh scattering is mostly neglected in calculations of hot star model atmospheres because most of the hydrogen atoms are ionized and the heavier elements…

Helium is the second-most abundant element in the Universe after hydrogen and is one of the main constituents of gas-giant planets in our Solar System. Early theoretical models predicted helium to be among the most readily detectable…

The quasiparticle propagation away from the track of a highly ionizing particle in superfluid helium at low temperatures has previously been shown to exhibit anisotropy. We discuss the mechanism responsible for this behavior and show that…

Only a small fraction of galactic nuclei in the nearby universe are luminous; most of them are currently dim. We investigate the feasibility of constraining the X-ray luminosity in the recent past (up to ~10^6 years ago) of the nucleus of a…

The differential cross section and the analyzing power are calculated for elastic scattering of $^6$He from a proton target using a microscopic folding optical potential, in which the $^6$He nucleus is described in terms of a $^4$He-core…

Deep inelastic neutron scattering experiments using indirect time-of-flight spectrometers have reported a smaller cross section for the hydrogen atom than expected from conventional scattering theory. Typically, at large momentum transfers,…