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Spectral Performance of Photon-Counting X-Ray Detectors
Published in Katsuyuki Taguchi, Ira Blevis, Krzysztof Iniewski, Spectral, Photon Counting Computed Tomography, 2020
Peter Trueb, Pietro Zambon, Christian Broennimann
The semiconductor sensor has an unstructured entrance side where a bias voltage is applied and a pixelated side with readout electrodes for every pixel. If a photon is absorbed by the photoelectric effect, its energy is transferred to an electron (known as photoelectron). This electron loses its energy by scattering with other electrons in the semiconductor sensor. Along its track the photoelectron thereby creates a large number of electron-hole pairs, which start to drift under the influence of the applied bias voltage. The generated amount of charge is proportional to the energy deposited in the sensor. In CdTe on average, one electron-hole pair is created per 4.4 eV. For a negative bias voltage the electrons are collected at the pixel electrode, while the holes drift to the unstructured side of the sensor.
Photon Interactions with Matter
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
In the photoelectric effect a photon interacts with an electron in an atom (Figure 5.1.3). If the energy of the incoming photon is high enough to overcome the binding energy of the electron, the electron may be ejected from the atom. That is, the atom is ionized. This ejected electron is called a photoelectron.
Monte Carlo Simulation in Diagnostic Radiology
Published in Richard L. Morin, Monte Carlo Simulation in the Radiological Sciences, 2019
In an atomic photoelectric effect, a photon is totally absorbed by a bound atomic electron, which is then ejected from the atom. Momentum is conserved by the recoil of the entire residual atom. Consequently, the most tightly bound electrons have the largest cross section of absorbing the incident photon. In order for the electrons in a certain atomic shell to participate in the photoelectric process, the incident photon must have an energy exceeding the electron binding energy of that shell. The absorption edges on the cross section curves reveal the participation of electrons from different shells as the photon energy increases. The photoelectron carries with it the energy of the absorbed photon minus the binding energy. This energetic electron, as it passes through the medium, gives rise to secondary ionization, excitation, and bremsstrahlung. However, for diagnostic photon energies, the electron range is usually much smaller (for example, about 0.13 mm in water for a 100 keV electron1) than the volume element used in the Monte Carlo calculations for the determination of the deposited energy, so that the diffusion of the electron can be neglected and its energy assumed to be absorbed locally.
Immunogenic antitumor potential of Prakasine nanoparticles in zebrafish by gene expression stimulation
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2023
X-ray photoelectron spectra were obtained using an ESCA + Omicron Nanotechnology ESCA Probe spectrometer (Scienta Omicron, Germany) with monochromatized aluminium K-alpha X-rays (energy: 1486.6 eV). The procedure was essentially as described in several previous studies [25–28]. Briefly, the X-ray power applied was 300 W, and the pass energy was 50 eV for survey scans and 20 eV for narrower specific regions. The sample solution was spotted on a molybdenum sample plate and dried in a vacuum. Spectra in the required binding energy ranges were collected and an average spectrum was constructed. Each spectrum was confirmed by replications (except the survey scan, which was performed only once). The scan rate (steps per second) was the same for all narrow scans. Beam-induced damage to the sample was reduced by adjusting the X-ray flux. The base pressure of the instrument was 5.0 × 10 − 10 mB.
Electronic properties of DNA-related molecules containing a bromine atom
Published in International Journal of Radiation Biology, 2023
Misaki Hirato, Misato Onizawa, Yuji Baba, Yoshinori Haga, Kentaro Fujii, Shin-ichi Wada, Akinari Yokoya
The XANES and XPS results showed that the photoelectron binding energies and the K-shell absorption energies of C, N, O, and P were similar, regardless of the presence of a Br atom. Because XANES spectra arise from the transition of the core electrons to the unoccupied level, information about the electronic state of the unoccupied level can be obtained. XPS measurements provide information about the electronic state of the core level by comparing the binding energies of photoelectrons. These results suggest that the Br atom does not contribute substantially to the electronic states of the molecules, particularly for the core level and LUMO, but does contribute to the state related to the excitation of the lattice vibration (oscillation and rotation in the molecule). In addition, we are currently investigating the effect of a Br atom on the valence electronic states involved in the chemical bond.
A comprehensive proteomics analysis of the response of Pseudomonas aeruginosa to nanoceria cytotoxicity
Published in Nanotoxicology, 2023
Lidija Izrael Živković, Nico Hüttmann, Vanessa Susevski, Ana Medić, Vladimir Beškoski, Maxim V. Berezovski, Zoran Minić, Ljiljana Živković, Ivanka Karadžić
A colloidal dispersion of ceria particles (sol) was characterized as detailed in previous work (Stevanović et al. 2020; Riđošić et al. 2021). X-ray diffraction (XRD) data confirmed that the synthesized CeO2 particles exhibited a fluorite-type crystal structure (space group: Fm3m, JCPDS 34-0394). The average crystallite size of ca. 4 nm, calculated according to the Scherrer equation, validated the method used to prepare the nano-sized ceria. X-ray photoelectron spectroscopy (XPS) is generally used to inspect the surface state of a material. Here, we report a significant amount (27%) of Ce3+ in CeO2 nanoparticles, along with prevailing Ce4+. As previously described, both Ce3+ and Ce4+ oxidation states are present in ceria particles, while the amount of Ce3+ increases with decreasing particle size.