NUCLEAR ISOMER EXCITATION BY LOW-ENERGY ELECTRONS AND X RAYS

1966 ◽  
pp. 236-237
Author(s):  
Benson T. Chertok
Keyword(s):  
Low Energy ◽  
X Rays ◽  
Low Energy Electrons ◽  
Nuclear Isomer

scholarly journals Auger Spectroscopy and Surface Analysis

1997 ◽  
Vol 50 (4) ◽  
pp. 745 ◽  
Author(s):  
S. M. Thurgate
Keyword(s):  
Short Distance ◽  
Auger Spectroscopy ◽  
Low Energy ◽  
Simultaneous Occurrence ◽  
X Rays ◽  
Auger Process ◽  
Surface Layers ◽  
Auger Electrons ◽  
Low Energy Electrons ◽  
Auger Spectra

Abstract In 1925 Pierre Auger reported on his observations of low energy electrons associated with core-ionised atoms in cloud chamber experiments. He was able to correctly identify the mechanism for their production, and such electrons are now known as Auger electrons. Typically Auger electrons have energies in the range 10 eV to 2 keV. The short distance that such low energy electrons travel in solids ensures that Auger electrons come from the surface layers. The data generated by the AES technique are complex. There are at least three electrons involved in the process, and there are many possible configurations for the atom. These possibilities led to spectra that are not readily interpreted in detail. Theory lags behind experiment in this area. In principle, it should be possible to find information about the chemical environment of atoms from Auger spectra. While there are clear changes in spectral lineshapes, there is no simple way to go from the spectra to an understanding of the chemical bonding of the atom. There are a number of experiments currently underway which aim to improve our understanding of the Auger process. Synchrotron experiments with tunable energy x-rays are providing new insight. Experiments that use positrons to excite Auger emission have also produced further recent understanding. Coincidence experiments between photoelectrons and Auger electrons have also made recent advances. Auger photoelectron coincidence spectroscopy reduces the complexity of Auger spectra by only counting those electrons that occur as a consequence of selected ionisations. The effect is to reduce the complexity of the spectra, and to isolate processes that are often clouded by the simultaneous occurrence of other effects.

On Lensless Imaging of Organics with Neutrons, X-Rays, Helium Atoms and Low Energy Electrons: Damage and Iterative Phase Retrieval

2001 ◽  
Vol 7 (S2) ◽  
pp. 268-269
Author(s):  
J.C.H. Spence ◽  
U. Weierstall ◽  
J. Fries
Keyword(s):  
Phase Retrieval ◽  
Iterative Algorithms ◽  
High Energy ◽  
Low Energy ◽  
X Rays ◽  
Noise Sources ◽  
Helium Atoms ◽  
High Energy Electrons ◽  
Elastic Event ◽  
Low Energy Electrons

Recent experiments with X-rays and high energy electrons have shown that image recovery from diffracted intensities is possible for non-periodic objects using iterative algorithms. Application of these methods to biological molecules raises the crucial problem of radiation damage, which may be quantified by Q = ΔE σi/σe, the amount of energy deposited by inelastic events per elastic event. Neutrons, helium atoms and low energy electrons below most ionization thresholds produce the smallest values of Q (see for TMV imaged at 60 eV). For neutrons (λ = 10-2Å, and deuterated, 15N-abelled molecules) Q is ∼3000 times smaller (∼50 times for λ = 1.8Å) than for electrons (80- 500keV) and about 4x 106 times smaller than for soft X-rays (1.5Å). Since σe for neutrons is about 105 times smaller than for electrons (and about 10 times smaller than for soft X-rays), a 105 times higher neutron dose is required to obtain the same S/N in a phase contrast image compared with electrons, if other noise sources are absent.

Spectra of low-energy electrons excited by soft x rays

1997 ◽  
Vol 42 (3) ◽  
pp. 318-321
Author(s):  
A. T. Kozakov ◽  
A. V. Nikol’skii
Keyword(s):  
Low Energy ◽  
X Rays ◽  
Low Energy Electrons

Aging of fluoropolymers irradiated by X-Rays, low energy electrons and energetic heavy ions

1986 ◽  
Vol 98 (1-4) ◽  
pp. 151-157 ◽  
Author(s):  
J. P. Duraud ◽  
A. Le Moël ◽  
C. Le Gressus
Keyword(s):  
Heavy Ions ◽  
Low Energy ◽  
X Rays ◽  
Low Energy Electrons

Stability of semiconducting transition metal dichalcogenides irradiated by soft X-rays and low energy electrons

2017 ◽  
Vol 110 (17) ◽  
pp. 173102 ◽  
Author(s):  
Roger C. Walker ◽  
Ganesh R. Bhimanapati ◽  
Tan Shi ◽  
Kehao Zhang ◽  
Sarah M. Eichfeld ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Low Energy ◽  
X Rays ◽  
Low Energy Electrons ◽  
Metal Dichalcogenides

scholarly journals Future Directions on Low-Energy Radiation Dosimetry

2021 ◽  
Author(s):  
G Massillon-JL
Keyword(s):  
Cross Sections ◽  
Density Functional ◽  
Absorbed Dose ◽  
Density Functional Theory Method ◽  
Point Of View ◽  
Low Energy ◽  
Sensitive Volume ◽  
X Rays ◽  
Starting Point ◽  
Low Energy Electrons

Abstract For more than one century, low-energy (< 100 keV) photons (x-rays and gamma) have been widely used in different areas including biomedical research and medical applications such as mammography, fluoroscopy, general radiography, computed tomography, and brachytherapy treatment, amongst others. It has been demonstrated that most of the electrons produced by low photon energy beams have energies below 10 keV. However, the physical processes by which these low energy electrons interact with matter are not yet well understood. Besides, it is generally assumed that all the energy deposited within a dosimeter sensitive volume is transformed into a response. But such an assumption could be incorrect since part of the energy deposited might be used to create defects or damages at the molecular and atomic level. Consequently, the relationship between absorbed dose and dosimeter response can be mistaken. During the last few years, efforts have been made to identify models that allow to understand these interaction processes from a quantum mechanical point of view. Some approaches are based on electron-beam − solid-state-interaction models to calculate electron scattering cross-sections while others consider the density functional theory method to localize low energy electrons and evaluate the energy loss due to the creations of defects and damages in matter. The results obtained so far could be considered as a starting point. This paper presents some methodologies based on fundamental quantum mechanics which can be considered useful for dealing with low-energy interactions.

Fluorescence imaging of reactive oxygen species by confocal laser scanning microscopy for track analysis of synchrotron X-ray photoelectric nanoradiator dose: X-ray pump–optical probe

2016 ◽  
Vol 23 (5) ◽  
pp. 1191-1196 ◽  
Author(s):  
Jae-Kun Jeon ◽  
Sung-Mi Han ◽  
Jong-Ki Kim
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Low Energy ◽  
Confocal Laser Scanning ◽  
Confocal Laser ◽  
Oh Radicals ◽  
X Rays ◽  
X Ray ◽  
Low Energy Electrons ◽  
Track Analysis

Bursts of emissions of low-energy electrons, including interatomic Coulomb decay electrons and Auger electrons (0–1000 eV), as well as X-ray fluorescence produced by irradiation of large-Zelement nanoparticles by either X-ray photons or high-energy ion beams, is referred to as the nanoradiator effect. In therapeutic applications, this effect can damage pathological tissues that selectively take up the nanoparticles. Herein, a new nanoradiator dosimetry method is presented that uses probes for reactive oxygen species (ROS) incorporated into three-dimensional gels, on which macrophages containing iron oxide nanoparticles (IONs) are attached. This method, together with site-specific irradiation of the intracellular nanoparticles from a microbeam of polychromatic synchrotron X-rays (5–14 keV), measures the range and distribution of OH radicals produced by X-ray emission or superoxide anions ({\rm{O}}_2^-) produced by low-energy electrons. The measurements are based on confocal laser scanning of the fluorescence of the hydroxyl radical probe 2-[6-(4′-amino)phenoxy-3H-xanthen-3-on-9-yl] benzoic acid (APF) or the superoxide probe hydroethidine-dihydroethidium (DHE) that was oxidized by each ROS, enabling tracking of the radiation dose emitted by the nanoradiator. In the range 70 µm below the irradiated cell, ^\bullet{\rm{OH}} radicals derived mostly from either incident X-ray or X-ray fluorescence of ION nanoradiators are distributed along the line of depth direction in ROS gel. In contrast, {\rm{O}}_2^- derived from secondary electron or low-energy electron emission by ION nanoradiators are scattered over the ROS gel. ROS fluorescence due to the ION nanoradiators was observed continuously to a depth of 1.5 mm for both oxidized APF and oxidized DHE with relatively large intensity compared with the fluorescence caused by the ROS produced solely by incident primary X-rays, which was limited to a depth of 600 µm, suggesting dose enhancement as well as more penetration by nanoradiators. In conclusion, the combined use of a synchrotron X-ray microbeam-irradiated three-dimensional ROS gel and confocal laser scanning fluorescence microscopy provides a simple dosimetry method for track analysis of X-ray photoelectric nanoradiator radiation, suggesting extensive cellular damage with dose-enhancement beyond a single cell containing IONs.

Sign in / Sign up

Export Citation Format

Share Document