scholarly journals Collisions in Strong Magnetic Fields

1987 ◽  
Vol 40 (1) ◽  
pp. 89 ◽  
Author(s):  
Michelle C Storey ◽  
DB Melrose
Keyword(s):  
Magnetic Fields ◽  
Cross Sections ◽  
Primary Source ◽  
Superstrong Magnetic Field ◽  
Electron Collisions ◽  
Proton Collisions ◽  
X Ray ◽  
Cyclotron Emission ◽  
Final Electron ◽  
Collision Processes

Exact cross sections for electron-electron collisions and electron-proton collisions in a superstrong magnetic field are derived using the QED formalism developed by Melrose and Parle. The results are compared with those of Langer who used a different QED formalism. The intended application is to collision processes in the accretion columns above neutron stars where magnetic fields of order 109 T are thought to be present. The particular case of electrons initially in their ground states, with one final electron in an excited state is described in detail; this process is thought to be the primary source of photons in X-ray pulsars, through subsequent cyclotron emission.

QED and X-Ray Pulsars

1985 ◽  
Vol 6 (2) ◽  
pp. 211-214 ◽  
Author(s):  
Michelle C. Allen ◽  
D. B. Melrose ◽  
A. J. Parle
Keyword(s):  
Neutron Stars ◽  
Cross Sections ◽  
Quantum Electrodynamics ◽  
Particle Interactions ◽  
Electron Collisions ◽  
X Ray ◽  
Electron Photon ◽  
Photon Interactions

AbstractTechniques in QED (quantum electrodynamics) have been developed previously (see for example Melrose and Parle 1983) allowing one to treat electron-photon and photon-photon interactions exactly in the magnetized vacuum and allowing one to include the effects of a medium. These techniques are extended to include particle-particle interactions. Exact cross-sections for electron-electron collisions are derived and compared with known expressions. Such calculations have application in studies of the formation and transfer of radiation in the atmospheres surrounding neutron stars.

Superstrong magnetic fields of neutron stars in Be X-ray binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 135-138
Author(s):  
ChangSheng Shi ◽  
ShuangNan Zhang ◽  
XiangDong Li
Keyword(s):  
Magnetic Fields ◽  
Neutron Stars ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Emission Lines ◽  
Disk Accretion ◽  
Superstrong Magnetic Field ◽  
X Ray ◽  
X Ray Binaries

AbstractA few Be X-ray binaries might constitute a group of special sources because the neutron stars in them may have superstrong magnetic fields. Generally, the neutron stars have long spin periods and some emission lines are shown from the B type star, which is attributed to an equatorial disc. We re-build new dimensionless torque models and obtain the superstrong magnetic fields of the neutron stars in the Be X-ray binaries in Large Magellanic Cloud, Small Magellanic Cloud and Milky Way when the compressed magnetosphere is considered. Although our conclusions are obtained when the disk accretion mode is considered, the results may be applied the Be X-ray binaries with wind accretion mode. SXP1323 and 4U 2206+54, in which the magnetic fields of the NSs may be close to the maximum ‘virial’ value, are the best objects to explore superstrong magnetic field.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

L X-RAY FLUORESCENCE CROSS-SECTIONS MEASUREMENTS FOR ELEMENTS 56≤Z≤66 IN THE ENERGY RANGE 11-41 keV

1987 ◽  
Vol 48 (C9) ◽  
pp. C8-669-C8-672 ◽  
Author(s):  
S. SINGH ◽  
S. KUMAR ◽  
D. MEHTA ◽  
M. L. GARG ◽  
N. SINGH ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
X Ray

Morphology and Affinities of Ampelocissites Seeds (Vitaceae: Ampelopsis clade) from the Paleogene of Texas, USA

2020 ◽  
Vol 45 (3) ◽  
pp. 478-482
Author(s):  
Steven R. Manchester
Keyword(s):  
Computed Tomography ◽  
Cross Sections ◽  
Seed Coat ◽  
Ct Scanning ◽  
Seed Morphology ◽  
Early Eocene ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Fossil Seeds ◽  
Fossil Genus

Abstract—The type material on which the fossil genus name Ampelocissites was established in 1929 has been reexamined with the aid of X-ray micro-computed tomography (μ-CT) scanning and compared with seeds of extant taxa to assess the relationships of these fossils within the grape family, Vitaceae. The specimens were collected from a sandstone of late Paleocene or early Eocene age. Although originally inferred by Berry to be intermediate in morphology between Ampelocissus and Vitis, the newly revealed details of seed morphology indicate that these seeds represent instead the Ampelopsis clade. Digital cross sections show that the seed coat maintains its thickness over the external surfaces, but diminishes quickly in the ventral infolds. This feature, along with the elliptical chalaza and lack of an apical groove, indicate that Ampelocissites lytlensis Berry probably represents Ampelopsis or Nekemias (rather than Ampelocissus or Vitis) and that the generic name Ampelocissites may be useful for fossil seeds with morphology consistent with the Ampelopsis clade that lack sufficient characters to specify placement within one of these extant genera.

scholarly journals Relativistic B-Spline R-Matrix Calculations for Electron Collisions with Ytterbium

Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 47
Author(s):  
Kathryn R. Hamilton ◽  
Klaus Bartschat ◽  
Oleg Zatsarinny
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Cross Sections ◽  
Matrix Method ◽  
Model Potential ◽  
Electron Collisions ◽  
R Matrix ◽  
B Spline ◽  
Potential Approach

We have applied the full-relativistic Dirac B-Spline R-matrix method to obtain cross sections for electron scattering from ytterbium atoms. The results are compared with those obtained from a semi-relativistic (Breit-Pauli) model-potential approach and the few available experimental data.

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

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