Photon Energies Of Order Research Articles

Probing optoelectronic and thermoelectric properties of double perovskite halides Li2CuInY6 (Y = Cl, Br, I) for energy conversion applications

Recently, double perovskite halides (DPHs) become crucial due to their potential applications in optoelectronic devices due to their stability, non-toxicity, superior oxidation resistance, high conversion efficiency, and high temperature stability. In the current study, we explored DPHs Li2CuInY6 (Y = Cl, Br, I) employing Wien2k package to analyze the structural stability, optoelectronic and thermoelectric features. The formation energy and Born stability criteria are computed to confirm thermodynamic and structural stability. Studied DPHs have direct bandgaps nature investigated by modified Becke and Johnson (mBJ) potential. Calculated values of bandgap decreases, when replace halide ion from Cl to I, indicate tuning from visible to infrared (IR) region of electromagnetic spectrum. Their band edge tuning across the visible to infrared border is reliant on replacement, which makes them suitable for projects involving opto-electronic devices. Further, optical features are investigated in terms of incident photon energy in order to assess the optical output. Lastly, electronic thermoelectric performance is computed using the figure of merit (ZT) for all DPs. Computed results of direct bandgap and optical behavior show that DP Li2CuInCl6 can be used as photovoltaic devices as compared to DPs Li2CuInBr6 and Li2CuInI6.

Site-specific interrogation of an ionic chiral fragment during photolysis using an X-ray free-electron laser

Short-wavelength free-electron lasers with their ultrashort pulses at high intensities have originated new approaches for tracking molecular dynamics from the vista of specific sites. X-ray pump X-ray probe schemes even allow to address individual atomic constituents with a ‘trigger’-event that preludes the subsequent molecular dynamics while being able to selectively probe the evolving structure with a time-delayed second X-ray pulse. Here, we use a linearly polarized X-ray photon to trigger the photolysis of a prototypical chiral molecule, namely trifluoromethyloxirane (C3H3F3O), at the fluorine K-edge at around 700 eV. The created fluorine-containing fragments are then probed by a second, circularly polarized X-ray pulse of higher photon energy in order to investigate the chemically shifted inner-shell electrons of the ionic mother-fragment for their stereochemical sensitivity. We experimentally demonstrate and theoretically support how two-color X-ray pump X-ray probe experiments with polarization control enable XFELs as tools for chiral recognition.

Chemical effects on the Li(i = l-3) sub-shell x-ray relative intensities for some compounds of Hg at 22.6 keV

The intensity ratios, ILk/ILα (exp) (k = 1, η, β4 6, β1,2,3,15, β5 7 9 10, γ1,5, γ2,3, γ4, β, γ) have been measured for some compounds of Hg80 namely, HgI2, HgBr2, Hg(C2H3O2)2 and a pure Hg80 target (liquid form) at 22.6 keV incident photon energy in order to investigate the influence of chemical effects on these ratios. The measured ratios, ILβ5,7/ILα(Exp.) and ILγ2,3,6/ILα(Exp.), were found to be influenced by chemical effects.

Chemical effects on the L i( i=1–3) sub-shell X-ray relative intensities for some compounds of Hg

The intensity ratios, I L k / I L α (exp) ( k= l, η, β 4,6, β 1,2,3,15, β 5,7, γ 1,5, γ 2,3,6,8, γ 4, β, γ), have been measured for some compounds of 80Hg, namely, HgI 2, Hg(C 2H 3O 2) 2 and a pure 80Hg target (liquid form) at 22.6 keV incident photon energy in order to investigate the influence of chemical effects on these ratios for a heavy transition element. The measurements have been performed using the EDXRF spectrometer involving a disk type radioactive source of Cd 109 and a Peltier cooled Si-PIN X-ray detector arranged in the 90° reflection geometry. The measured intensity ratios have been compared with the theoretical I L k / I L α (Thr.) values ( Kumar et al., 2010) and those calculated using the fluorescence and Coster–Kronig yields tabulated by Campbell (2003, 2009) and Krause (1979) in order to check the reliability of these available values. The measured ratios, I L β5,7 / I L α (Exp.), were found to be influenced by the chemical effects.

Pareto front analysis of 6 and 15 MV dynamic IMRT for lung cancer using pencil beam, AAA and Monte Carlo

The pencil beam dose calculation method is frequently used in modern radiation therapy treatment planning regardless of the fact that it is documented inaccurately for cases involving large density variations. The inaccuracies are larger for higher beam energies. As a result, low energy beams are conventionally used for lung treatments. The aim of this study was to analyze the advantages and disadvantages of dynamic IMRT treatment planning for high and low photon energy in order to assess if deviating from the conventional low energy approach could be favorable in some cases. Furthermore, the influence of motion on the dose distribution was investigated. Four non-small cell lung cancer cases were selected for this study. Inverse planning was conducted using Varian Eclipse. A total number of 31 dynamic IMRT plans, distributed amongst the four cases, were created ranging from PTV conformity weighted to normal tissue sparing weighted. All optimized treatment plans were calculated using three different calculation algorithms (PBC, AAA and MC). In order to study the influence of motion, two virtual lung phantoms were created. The idea was to mimic two different situations: one where the GTV is located centrally in the PTV and another where the GTV was close to the edge of the PTV. PBC is in poor agreement with MC and AAA for all cases and treatment plans. AAA overestimates the dose, compared to MC. This effect is more pronounced for 15 than 6 MV. AAA and MC both predict similar perturbations in dose distributions when moving the GTV to the edge of the PTV. PBC, however, predicts results contradicting those of AAA and MC. This study shows that PB-based dose calculation algorithms are clinically insufficient for patient geometries involving large density inhomogeneities. AAA is in much better agreement with MC, but even a small overestimation of the dose level by the algorithm might lead to a large part of the PTV being underdosed. It is advisable to use low energy as a default for tumor sites involving lungs. However, there might be situations where it is favorable to use high energy. In order to deviate from the recommended low energy convention, an accurate dose calculation algorithm (e.g. MC) should be consulted. The study underlines the inaccuracies introduced when calculating dose using a PB-based algorithm in geometries involving large density variations. PBC, in contrast to other algorithms (AAA and MC), predicts a decrease in dose when the density is increased.

Image quality in mammography: physical and technical limitations.

Special imaging problems arise in mammography since the conditions are quite different from those in other fields of radiology. The differences in attenuation of the various soft tissue structures in the female breast are small, and it is necessary to use X-rays with low photon energy in order to get a sufficiently high contrast in the mammographic film. Jennings and Fewell (1979) examined the relative exposure necessary to achieve a constant signal-to-noise ratio for various photon energies. They found a minimum at approximately 20 keV, when glandular tissue in the breast was imaged. Moreover, small details such as microcalcifications may have diameters no larger than 0.1 mm and can only be imaged using a system with high spatial resolution. Although microcalcifications have high attenuation, their small dimensions along the direction of the X-ray beam reduce their attenuation so that it is necessary to use a system giving high contrast.

Excitation energy dependence in the photoemission satellite structures in solid CO and N2

We use the relative intensity of photoemission satellites in the outer core, inner valence region measured as a function of photon energy in order to identify the spectroscopic assignment for each individual satellite. The outer valence satellites show a decrease in intensity relative to the outer valence single particle emission over the excitation energy range from 40 to 140 eV. The 3σ(2σg) derived structures, on the other hand, increase in intensity, measured relative to the outer valence emission as expected from the general behavior of the 3σ(2σg) single particle cross section.