shell ionization
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2022 ◽  
Vol 2155 (1) ◽  
pp. 012030
Author(s):  
G.A. Abdullaeva ◽  
G.A. Kulabdullaev ◽  
A.A. Kim ◽  
A.F. Nebesny ◽  
D.O. Yuldashev

Abstract In this study, we evaluate the features of dose enhancement with Gd contrast agent (Magnevist). Due to the increased relaxation time and high atomic number (z=64) Gd can be used in radiation therapy as a radiosensitizer. To perform a quantitative evaluation of the radiosensitization effect is determined a parameter called the dose enhancement factor - DEF. The DEF values were calculated based on the analysis of the mass absorption coefficients for gadolinium and biological tissue. An increase in DEF is observed when the radiation energy is higher than the K-shell ionization energy of Gd atoms. For the presence of 20315 ppm Gd contrast agent in biological tissue the dose enrichment factor is maximum DEF = 4.12 at photon irradiation energy 60 keV. Also, based on calculations for photon irradiation sources considered high degrees of dose enhancement occur for Am-241, Yb-196, and 100 kVp X-ray tube.


2022 ◽  
Vol 232 ◽  
pp. 113401
Author(s):  
F. Fernandez ◽  
A. Sepúlveda ◽  
J. Trincavelli ◽  
G. Castellano

2021 ◽  
Author(s):  
Xian-Ming Zhou ◽  
Jing Wei ◽  
Rui Cheng ◽  
Yan-Hong Chen ◽  
Ce-Xiang Mei ◽  
...  

Abstract The L-shell x ray of Nd has been obtained for 300 - 600 keV He2 + ions impacting, and compared with that produced by H+ and H2 + ions. The threshold of projectile kinetic energy for L-shell ionization of Nd is crudely verified in the energy region of about 300 - 400 keV. It is found that the energy of the distinct L-subshell x rays has a blue shift. The relative intensity ratios of Lβ1, 3, 4 and Lβ2, 15 to Lα1, 2 x-ray are enlarged compared to the atomic data, and they decrease with the increase of incident energy, and increase with increasing effective nuclear charge of the incident ions. That is interpreted by the multiple ionization of outer-shells induced by light ions.


Author(s):  
David Vogel ◽  
Peter Beiersdorfer ◽  
Keith Wong ◽  
Ron Zasadzinski ◽  
Ming Feng Gu

We present relative cross section measurements of the inner-shell ionization of highly charged chromium ions by high-energy (7-30 keV) electrons. The measurements use a technique based on high-resolution x-ray spectroscopy, which correlates ionization events with K∝ decay x rays. Moreover, the measurements show that inner-shell ionization only affects the strength of the heliumlike 1s2s 3S1 -> 1s2 1S0 forbidden line. The cross sections inferred for Li-like Cr21+ agree well with distorted wave calculations.


Author(s):  
Kannan M. Krishnan

We review the structure of atoms to describe allowed intra-atomic electronic transitions following dipole selection rules. Inner shell ionization is followed by characteristic X-ray emission or non-radiative de-excitation processes leading to Auger electrons that involve three atomic levels. Photon incidence also results in characteristic photoelectron emission, reflecting the energy distribution of the electrons in the solid. We present details of laboratory and synchrotron sources of X-rays, and discuss their detection by wavelength or energy-dispersive spectrometers, as well as microanalysis with X-ray (XRF), or electron (EPMA) incidence. Characteristic X-ray intensities are quantified in terms of composition using corrections for atomic number (Z), absorption (A), and fluorescence (F). Electron detectors use electrostatic or magnetic dispersing fields; two common designs are electrostatic hemispheric or mirror analyzers. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), used for surface analysis, require ultra-high vacuum. AES is a weak signal, best resolved in a derivative spectrum, shows sensitivity to the chemical state and the atomic environment, provides a spatially-resolved signal for composition mapping, and can be quantified for chemical analysis using sensitivity factors. Finally, we introduce the basics of XPS, a photon-in, electron-out technique, discussed further in §3.


Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 520
Author(s):  
Stephan Fritzsche ◽  
Patrick Palmeri ◽  
Stefan Schippers

Atomic cascades are ubiquitous in nature and they have been explored within very different scenarios, from precision measurements to the modeling of astrophysical spectra, and up to the radiation damage in biological matter. However, up to the present, a quantitative analysis of these cascades often failed because of their inherent complexity. Apart from utilizing the rotational symmetry of atoms and a proper distinction of different physical schemes, a hierarchy of useful approaches is therefore needed in order to keep cascade computations feasible. We here suggest a classification of atomic cascades and demonstrate how they can be modeled within the framework of the Jena Atomic Calculator. As an example, we shall compute within a configuration-average approach the stepwise decay cascade of atomic magnesium, following a 1s inner-shell ionization, and simulate the corresponding (final) ion distribution. Our classification of physical scenarios (schemes) and the hierarchy of computational approaches are both flexible to further refinements as well as to complex shell structures of the atoms and ions, for which the excitation and decay dynamics need to be modeled in good detail.


2021 ◽  
Vol 180 ◽  
pp. 109321
Author(s):  
S. Liang ◽  
Y. Wu ◽  
Z. Zhao ◽  
X.G. Xia ◽  
Z.X. Ke ◽  
...  

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