982 research outputs found
Three-body treatment of the penetration through the Coulomb field of a two-fragment nucleus
On the basis of the Faddeev integral equations method and the Watson-
Feshbach concept of the effective (optical) interaction potential, the first
fully consistent three-body approach to the description of the penetration of a
charged particle through the Coulomb field of a two-particle bound complex
(composed of one charged and one neutral particles) has been developed. A
general formalism has been elaborated and on its basis, to a first
approximation in the Sommerfeld parameter, the influence of the nuclear
structure on the probability of the penetration of a charged particle (the
muon, the pion, the kaon and the proton) through the Gamow barrier of a
two-fragment nucleus (the deuteron and the two lightest lambda hypernuclei,
lambda hypertriton and lambda hyperhelium-5, has been calculated and studied.Comment: LaTeX, 30 pages, 4 eps figure
OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions
We study the 0.57 keV (O VII triplet) and 0.65 keV (O VIII) diffuse emission
generated by charge transfer collisions between solar wind (SW) oxygen ions and
interstellar H and He neutral atoms in the inner Heliosphere. These lines which
dominate the 0.3-1.0 keV energy interval are also produced by hot gas in the
galactic halo (GH) and possibly the Local Interstellar Bubble (LB). We
developed a time-dependent model of the SW Charge-Exchange (SWCX) X-ray
emission, based on the localization of the SW Parker spiral at each instant. We
include input SW conditions affecting three selected fields, as well as
shadowing targets observed with XMM-Newton, Chandra and Suzaku and calculate
X-ray emission fot O VII and O VIII lines. We determine SWCX contamination and
residual emission to attribute to the galactic soft X-ray background. We obtain
ground level intensities and/or simulated lightcurves for each target and
compare to X-ray data. The local 3/4 keV emission (O VII and O VIII) detected
in front of shadowing clouds is found to be entirely explained by the CX
heliospheric emission. No emission from the LB is needed at these energies.
Using the model predictions we subtract the heliospheric contribution to the
measured emission and derive the halo contribution. We also correct for an
error in the preliminary analysis of the Hubble Deep Field North (HDFN).Comment: 21 pages (3 on-line), 10 figures (4 on-line), accepted for
publication in Astronomy and Astrophysic
Theory and simulation of spectral line broadening by exoplanetary atmospheric haze
Atmospheric haze is the leading candidate for the flattening of expolanetary
spectra, as it's also an important source of opacity in the atmospheres of
solar system planets, satellites, and comets. Exoplanetary transmission
spectra, which carry information about how the planetary atmospheres become
opaque to stellar light in transit, show broad featureless absorption in the
region of wavelengths corresponding to spectral lines of sodium, potassium and
water. We develop a detailed atomistic model, describing interactions of atomic
or molecular radiators with dust and atmospheric haze particulates. This model
incorporates a realistic structure of haze particulates from small nano-size
seed particles up to sub-micron irregularly shaped aggregates, accounting for
both pairwise collisions between the radiator and haze perturbers, and
quasi-static mean field shift of levels in haze environments. This formalism
can explain large flattening of absorption and emission spectra in haze
atmospheres and shows how the radiator - haze particle interaction affects the
absorption spectral shape in the wings of spectral lines and near their
centers. The theory can account for nearly all realistic structure, size and
chemical composition of haze particulates and predict their influence on
absorption and emission spectra in hazy environments. We illustrate the utility
of the method by computing shift and broadening of the emission spectra of the
sodium D line in an argon haze. The simplicity, elegance and generality of the
proposed model should make it amenable to a broad community of users in
astrophysics and chemistry.Comment: 16 pages, 4 figures, submitted to MNRA
- …