Low-energy Photons Research Articles

Direct Evidence for Preburst Stage of Gamma-Ray Burst from GRB 221009A Data

Previous research on Lorentz invariance violation in photons from gamma-ray bursts (GRBs) suggested a scenario where multi-GeV photons could be emitted before lower-energy photons at the GRB source frame. This implies the existence of a new preburst phase in addition to the traditionally identified prompt and afterglow stages observed in earlier studies. In this study, we present direct evidence for this novel preburst phase in GRBs based on recent observations of GRB 221009A. Our analysis leverages data from the Fermi Gamma-ray Burst Monitor and Large Area Telescope detectors of the Fermi Gamma-ray Space Telescope, as well as data from the KM2A detector of the Large High Altitude Air-shower Observatory.

Predictions on new Cu-based ABO3 (A=Cu and B=Lu, Y) oxide-perovskite for energy storage and optoelectronic applications: A DFT study

Cu-based novel oxide-perovskite ABO3(A = Cu and B=Lu, Y) compounds have been investigated for their physical properties using the Generalized Gradient Approximation and Revised-Perdew-Burke-Ernzerhof (GGA-RPBE) exchanging correlation-functional within the density functional theory (DFT). The calculations show that both compounds comprise a cubic structure with the space group of Pm3m. The calculations also indicate that the results we have discovered represent unique compounds. Formation enthalpy computations have been used to assess the overall structural stability of both compounds. The density of states and band structure graphs for both perovskite compounds provide strong evidence of their semiconducting behavior. In-depth research is also done on optical properties such as the refractive index, extinction coefficient, absorption, reflectivity, electrical conductivity, and the energy loss function. At high-energy photons, both compounds CuLuO3 and CuYO3 show outstanding conductivity and absorption. While, at lower incident photon energy intervals, they both exhibit transparency. Based on our electronic and optical properties investigations, we have found that CuLuO3 and CuYO3 are potential candidates for use in high-energy UV, and optoelectronic technologies.

Attenuation coefficients of soy-lignin bonded Rhizophora spp. particleboard as a potential phantom material using Monte Carlo GATE

This work aimed to determine the linear and mass attenuation coefficients of soy-lignin bonded Rhizophora spp. particleboard intended for use as a phantom material using Monte Carlo GATE simulation. At a desired density of 1.0 gcm-3, particleboard constructed of Rhizophora spp. wood trunk bonded with soy flour and lignin was created. The sample’s elemental composition was identified using energy dispersive X-ray spectroscopy. The GATE software was used to simulate the setup with the histories of 1 × 107, and comparison was made between the experimental and simulation data. The disparities between the linear and mass attenuation coefficients of the samples experimentally measured and calculated using GATE at low energy photons were quite small. The result revealed a good agreement between the experimental and simulation data, and the attenuation coefficients were in close proximity with XCOM of water. The outcome revealed GATE adequacy for validation of attenuation coefficient measurement in bioresources phantom material for medical physics application.

Broadband self-powered MoS2/PdSe2/WSe2 PSN heterojunction photodetector for high-performance optical imaging and communication.

Two-dimensional (2D) semi-metal transition metal dichalcogenides (TMDs) have drawn significant attention for their distinctive physical properties. However, the inherent high dark current of these materials and the single structure of detectors hinder the further development of photodetectors with high performance. Here, we construct a PSN (p-type semiconductor/semi-metal/n-type semiconductor) architecture by sandwiching 2D semi-metal between two semiconductor layers. In this architecture, the top and bottom layers generate an internal built-in electric field, while the middle layer serves as an absorption layer for low-energy photons and facilitates the dissociation of photo-generated carriers. As a result, the heterojunction device demonstrates a wide spectrum optical response from visible to infrared light (405 nm to 1550 nm) without requiring an external voltage. Working in self-powered mode at room temperature, the device achieves a responsivity of 0.56 A/W, a detectivity of 5.63 × 1011 Jones, and a rapid response speed of 190/74 µs. Additionally, the device shows potential for applications in fast optical communication and multi-wavelength optical imaging. This work presents a novel approach for developing a new type of broadband, self-powered, high-performance miniaturized semi-metal-based photodetector.

Large depth-of-focus achievement based on an aspheric lens with a ring

Terahertz (THz) imaging technology has been widely studied because of its easy penetration of non-polar materials and low photon energy. To acquire a beam featuring both excellent transverse spatial resolution and a considerable depth-of-focus (DOF) to fulfill the demands of two-dimensional and three-dimensional THz imaging, this paper presents an aspheric lens with ring (ALR). The ALR has a controlled diameter of 50 mm, can be machined by 3D-printed technology, and does not need to use complex imaging optical paths to achieve the large DOF function. In a transmitted point-scan imaging system with a 140 GHz light source, the lens can achieve both a resolution of 6 mm and an effective DOF of 66.4 mm for objects greater than 27 mm from the lens surface.

Anion-Driven Bandgap Tuning of AgIn(SxSe1-x)2 Quantum Dots.

Accurate tuning of the electronic and photophysical properties of quantum dots is required to maximize the light conversion efficiencies in semiconductor-assisted processes. Herein, we report a facile synthetic procedure for AgIn(SxSe1-x)2 quantum dots with S content (x) ranging from 1 to 0. This simple approach allowed us to tune the bandgap (2.6-1.9 eV) and extend the absorption of AgIn(SxSe1-x)2 quantum dots to lower photon energies (near-IR) while maintaining a small QD size (∼5 nm). Ultraviolet spectroscopy studies revealed that the change in the bandgap is modulated by the electronic shifts in both the valence band and the conduction band positions. The negative overall charge of the as-synthesized quantum dots enabled us to make films of quantum dots on mesoscopic TiO2. Excited state studies of the AgIn(SxSe1-x)2 quantum dot films demonstrated a fast charge injection to TiO2, and the electron transfer rate constant was found to be 1.5-3.5 × 1011 s-1. The results of this work present AgIn(SxSe1-x)2 quantum dots synthesized by the one-step method as a potential candidate for designing light-harvesting assemblies.

Radiation Shielding Properties of Nickel, Copper and Iron Based Alloys

This study explores the radiation shielding properties of Iron-based and Nickel-based alloys with Cobalt composition to evaluate their performance in photon attenuation and shielding applications. The objectives of this work are to determine linear and mass attenuation coefficients (LAC, MAC), half and tenth value layers (HVL, TVL), mean free path (MFP), effective atomic number and electron density (Zeff, Neff), effective conductivity (Ceff), atomic cross section (ACS) and electronic cross section (ECS) of nickel and iron base alloy with Cobalt using Phy-X/PSD within 0.001 MeV to 10 MeV. The result shows Iron and Nickel-based alloys have electron densities around 10²³ electrons per gram, with increased Iron concentration improving low-energy photon attenuation. Nickel-based alloys have a higher MAC and LAC compared to Iron-based oxides, indicating better photon absorption per unit mass and thickness, respectively. Nickel-based alloys exhibit a lower HVL and TVL, indicating greater attenuation and absorption efficiency for photons, especially at lower energies. Conversely, Iron-based alloys, while showing higher HVL and TVL. Nickel-based alloys exhibited higher electron densities the Iron-based alloys and Zeff values for Nickel based alloys, ranging from 27.1 to 27.8 while Iron-based alloys with Zeff between 26.2 and 26.8. Ceff in Iron-based alloys was stable at (1.50 to 1.74) x 10⁹ S/m, while Nickel-based alloys showed significant fluctuations below 0.01 MeV. Nickel-based alloys also had higher ACS and ECS, indicating superior photon interaction, especially at lower energies. These results highlight Nickel based alloys' greater efficacy in low-energy photon attenuation and the stable performance of Iron based alloys at higher energies.

Nickel oxide nanoparticles embedded in polymer-matrix nanocomposite prepared by nanosecond laser ablation method for optoelectronic applications

The polymeric PVA structure embedded with nickel oxide nanoparticles (NiO NPs) was synthesized using nanosecond pulsed laser ablation in liquid media technique for optoelectronic applications. A comprehensive investigation was conducted on the optical and electrical characteristics of the fabricated films to demonstrate the proficiency of the proposed nanocomposite film in that particular domain. Different weights of NiO nanoparticles were generated by embedding them in PVA film using different ablation durations. It was shown that as the concentration of NiO embedded in PVA increased in correlation with the ablation period, the absorption peak changed to a longer wavelength, and the absorption edge of PVA changed towards lower photon energy with a reduction in the band gap density. Followed by the increase in disorder degree through the addition of NiO NPs, while an average value of the dispersion energy is identical, and the nonlinear parameters (χ(3) and n2) increase. Also, the results emphsies that the dielectric characteristics were affected as the concentration of NiO NPs increased due to the rise in the density of states, which resulted in the generation of polarization. Due to the creation of the charge transfer complex, the optical conductivity of the produced nanocomposites rises as the concentration of NiO NPs increases. Therefore, the optical and electrical characteristics of PVA are significantly affected by the incorporation of NiO nanocomposites.

Development of a Monte Carlo simulation platform for the systematic evaluation of photon-counting detector-based micro-CT

PurposeThis study aimed to develop a photon-counting detector (PCD) based micro-CT simulation platform for assessing the performance of three different PCD sensor materials: cadmium telluride (CdTe), gallium arsenide (GaAs), and silicon (Si). The evaluation encompasses the components of primary and scatter signals, performance of imaging contrast agents, and detector efficiency. MethodsSimulations were performed using the Geant4 Monte Carlo toolkit, and a micro-PCD-CT system was meticulously modeled based on realistic geometric parameters. Results.The simulation can obtain HU values consistent with measured results for iodine and calcium hydroxyapatite contrast agents. The two major components of scatter signals for CdTe and GaAs based PCD are fluorescent X-ray photons and photoelectrons, whereas for Si, the components are photoelectrons and Compton electrons. Scattering counts of CdTe and GaAs sensors can be effectively reduced by using energy thresholds, whereas those of Si sensor are insensitive to the applied threshold. The optimal threshold values for CdTe and GaAs are 30 and 15 keV, respectively. For contrast agent imaging, GaAs exhibits enhanced sensitivity to low photon energies compared to CdTe, while it’s contrast-to-noise ratio (CNR) values are slightly lower than those of CdTe at the same contrast agent concentration. Among the three sensor materials, Si has the lowest CNR and detector efficiency; CdTe exhibits the highest efficiency, except in low-energy ranges (< 45 keV), where GaAs has superior efficiency. ConclusionsThe proposed methods are expected to benefit PCD optimization and applications, including energy threshold selection, scattering correction, and may reduce the need for large-scale experiments.

Investigating the optoelectronic properties of Mn and Fe doped CuAlS₂ for intermediate band solar cell applications

Chalcopyrites demonstrate compelling features for optoelectronic and photovoltaic devices, attributed to their valuable properties. Their remarkable light-absorption capabilities and well-suited band gap render them so attractive for applications in these fields. By allowing low-energy sub-bandgap photons to pass through and reducing the thermalisation loss from high-energy photons, intermediate-band materials address the primary problems in solar cells. This approach allows for more efficient use of the solar spectrum, helping solar cells exceed the traditional efficiency limits defined by the Shockley-Queisser limit. The objective of this study was to evaluate the electronic and optical characteristics of CuAlS2 systems doped with transition metals (TM = Mn, Fe) using the Full Potential Linearized Augmented Plane Wave approach within the framework of Density Functional Theory. A stable phase within the systems was observed upon replacing the Al atom with TM. The functionality of the intermediate band was governed by the 3d electronic characteristics of the TM3+ ion and its electronic configuration. The optical properties of CuAlS2 doped with Mn and Fe were analysed by calculating the dielectric function, refractive index, reflectivity, and absorption coefficient. Furthermore, the introduction of Mn and Fe through doping led to the creation of an intermediate band, enhancing visible light absorption and power conversion efficiency. Consequently, the optical spectrum of Mn-doped CuAlS2 and Fe-doped CuAlS2 compounds exhibits additional absorption peaks, accompanied by a significant improvement in absorption intensity. Our findings highlighted the need for continued and futuristic research into the scalability of these materials for practical applications in solar cells, optoelectronics, and spintronic devices. This investigation suggests that Mn-doped CuAlS2 holds the highest potential due to its high charge carriers and low recombination rate, indicating enhanced performance in CuAlS2-based intermediate band solar cells.

Synthesis and characterization of metakaolin-based geopolymers doped with CRT waste glass for radiation shielding applications

This study presents the influence of CRT glass on the gamma-ray interaction processes in metakaolin-based geopolymers. Four batches of G-CRT composites (namely, G, G-10CRT, G-20CRT, and G-30CRT, which represent geopolymer (G) samples doped with 0, 10, 20, and 30 wt% of CRT glass) were prepared using the cold hydrostatic press method. The mass attenuation coefficients of the prepared C-xCRT samples were computed using XCOM and FLUKA simulations for photons within the energy range of 15 keV–15 MeV. The density of the pristine geopolymer increased from about 1.86 g/cm3 to 2.09, 2.26, and 2.34 g/cm3 for G-10CRT, G-20CRT, and G-30CRT, respectively. The photon mass and linear attenuation coefficients of the geopolymers increased with CRT glass concentration. The half-value layer and mean free path were within the ranges 0.070–18.079 cm and 0.101–26.083 cm for G; 0.036–15.110 cm and 0.052–21.799 cm for G-10CRT; 0.024–13.197 cm and 0.014–19.039 cm for G-20CRT; and 0.018–12.074 and 0.026–17.419 cm for G-30CRT. The G-30CRT had the best gamma attenuating prowess in contrast to other G-xCRT. CRT-rich G-xCRT had a higher effective atomic number. For 10 mm thick geopolymer, the absorbed dose rates were 0.211 μR/h, 0.66 μR/h, 1.11 μR/h, and 1.55 μR/h for G, G-10CRT, G-20CRT, and G-30CRT, respectively, for 100 keV photons. The introduction of CRT glass into the geopolymer matrix improved their photon interaction cross-section. The geopolymers showed outstanding photon interaction ability compared to ordinary concrete and some shielding glasses at low photon energies. The CRT glass-doped geopolymer samples are useful for preparing radiation shielding concrete.

A π−π stacked porous framework for highly efficient second near-infrared photothermal effects and photo-thermo-electric conversion

Near-infrared (NIR) photothermal compounds, which convert low-energy NIR photons into heat, have recently attracted significant attention due to their potential applications in many areas such as photothermal imaging, diagnosis and therapy, photosensors, and catalysis. Photothermal conversion efficiency (PCE), a critical parameter of NIR photothermal materials, significantly influences their practical performance. However, exploring highly efficient NIR photothermal compounds, particularly in the NIR-II domain, remains a significant challenge. Herein, we report on a highly efficient NIR-II photothermal compound based on a novel π−π stacked porous framework {[Ni4Cl2(ONDI)2(bpy)4]⋅2Cl⋅2H2O⋅xDMF⋅yH2O}n (1). This compound features a porous supramolecular framework constructed through intermolecular π−π interactions. Additionally, compound 1 exhibits broad optical absorption spanning from the ultraviolet to the NIR region, with an edge extending to 1600 nm. Under irradiation with a 1064 nm laser, compound 1 demonstrates significant NIR-II photothermal effects, achieving a remarkable PCE of 84.4 %, attributed to the formation of charge states and the abundant π−π interactions in its crystal structure. When integrated with commercial thermoelectric generators, compound 1 shows promising potential for photo-thermo-electric conversion, with a maximum open-circuit voltage of 250 mV and 350 mV under irradiation of 1 sun and 2 suns, respectively. Furthermore, the output power density of 1@TEC1-12701 reaches 0.53 W/m2 under 1 sun and 1.23 W/m2 under 2 suns.

Triplet-Triplet Annihilation-Based Photon Upconversion with a Macrocyclic Parallel Dimer.

The integration of multiple chromophore units into a single molecule is expected to improve the performance of photon upconversion based on triplet-triplet annihilation (TTA-UC) that can convert low energy photons to higher energy photons at low excitation intensity. In this study, a macrocyclic parallel dimer of 9,10-diphenylanthracene (DPA) with a precisely parallel orientation, named MPD-2, is synthesized, and its TTA-UC properties are investigated. MPD-2 shows a green-to-blue TTA-UC emission in the presence of a triplet sensitizer, platinum octaethylporphyrin (PtOEP). Compared to monomeric DPA, MPD-2 results in an enhancement of the spin statistical factor of TTA and a decrease in the excitation light intensity due to the intramolecular TTA process. The obtained structure-property relationship provides important information for the further improvement of TTA-UC properties.

Intensity-energy response function of Al/Cr-K[formula omitted] x-ray photoemission instruments: An inter-laboratory study

The question of the intensity-energy response of photoemission spectrometers has been approached through a round-robin involving 13 instruments working with low (Al/Mg-Kα) and high (Cr-Kα) energy photon sources. An algorithm based on the analysis of inelastic background previously proposed [S. Guilet et al., J. Electron Spectrosc. Relat. Phenom. 285 (2022) 147225)] was intensively tested against calibrated Al/Mg-Kα instruments and calculated relative sensitivity factors (RSFs) over the 15 core level peaks of coinage metals (Ag, Au, Cu). In both cases, the linear correlation within ±10 %, over two orders of magnitude in intensity and for kinetic energies ranging from ∼400 to 1400eV, showed the consistency of the approach. All the contributions to RSFs (e.g. non-dipolar terms in the photo-ionization cross section, elastic scattering effects, surface excitations, beam polarization by the monochromator) were critically reviewed and taken into account using the state-of-the-art modellings and databases. Strong variations were evidenced among instruments, regarding not only the response functions, but also the theoretical RSFs due to different measurement geometries. For the Cr-Kα hard x-ray instruments, the same analysis was performed with a set of different materials (Al, Si, Ge, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ag, W, Au). A ±10 % satisfactory agreement against theoretical RSFs over 69 core levels spanning a large kinetic energy range (300–4000 eV) could be achieved with a common response function. Despite limitations that are reviewed, this work opens interesting perspectives for a systematic calibration of photoemission instruments.

Ionic Fragmentation of the Halothane Molecule Induced by EUV and Soft X-ray Radiation.

EUV and soft X-ray-induced photofragmentation of the halothane (CF3CHBrCl) molecule has been investigated using time-of-flight mass spectrometry in the coincidence mode (PEPICO) covering the valence region and vicinity of the bromine 3d, chlorine 2p, and carbon 1s edges. Total and partial ion yields have been recorded as a function of photon energy. At lower photon energies, the heavier singly charged molecular fragments predominate in the mass spectra. On the other hand, there is a strong tendency to the atomization of the molecule at higher photon energies. Despite the different chemical environments experienced by the two carbon atoms, weak site-specific fragmentation is observed. In addition, ab initio quantum mechanical calculations at the MP2 level and a series of computations with multiconfigurational self-consistent field have been performed to describe the inner-shell states.

Radiation Shielding Analysis of Multi-Component Glasses: Effects of Varying BaO, PbO2 and Gd2O3 Concentrations

This work investigates the impact of BaO, PbO2, and Gd2O3 on newly developed borate glasses’ radiation shielding characteristics. The transmission factor (TF) of the glasses is almost zero at the low energy of 0.0395 MeV, which indicates favorable low-energy photon shielding. The maximum TF is reported at 1.46 MeV for the free Gd2O3 glass sample, ranging from 0.89 (0.5 cm thickness) to 0.73 (1.5 cm thickness). Moreover, with more BaO, PbO2, and Gd2O3 content added to the glasses, the TF decreases, indicating an enhancement in the efficiency of the glasses’ radiation protection with the introduction of BaO, PbO2, and Gd2O3. There is a 4.309 to 5.068 g cm−3 increase in the glasses’ density, and, as a result, the mean free path decreases, suggesting improved performance for radiation protection with the adding of more BaO, PbO2, and Gd2O3 contents to the glasses. At 0.122 MeV, the free Gd2O3 glass’s half value layer value is 0.098 cm, while the tenth value layer is 0.325 cm.

Influence of the clay fractions from various horizons on the radiation shielding parameters of an Arenosol

AbstractThis study examines the effects of the chemical composition of the clay fraction of various soil horizons on radiation shielding parameters. X-ray fluorescence (XRF) analysis did not reveal significant differences in the concentration of the most abundant oxides (Al2O3, SiO2, Fe2O3) among the various horizons. Consequently, the mass attenuation coefficient did not vary among the horizons in terms of the photon energies studied (15 keV–10 MeV). The mean free path (MFP), half-value layer (HVL) and tenth-value layer (TVL) did not differ for energies up to 100 keV. However, at higher energies, these parameters were mainly influenced by the differences in the densities of the soil horizons. The effective atomic number did not differ across the horizons for the various photon energies, nor did the mass attenuation coefficient. It is shown that slight differences in the chemical composition of the clay fraction of soil horizons do not affect radiation shielding parameters (MFL, HVL, TVL) for low photon energies (&lt;500 keV). Density is more important for radiation shielding than the chemical composition of the various horizons of the same soil type for higher energies (&gt;100 keV); hence, compacting the clay fraction might be more efficient for radiation shielding purposes at higher energies.

Photon upconversion immunoprobe based on resonance energy transfer for brain natriuretic peptide – A prognostic biomarker for heart failure

Brain Natriuretic Peptide (BNP) holds significant clinical importance as a biomarker for heart-related conditions aiding in diagnosis, prognosis and monitoring of heart failure, providing valuable insights for timely intercession and patient management. Photon upconversion nanomaterials exhibit captivating ability to convert low energy photons to high energy ones, enabling enhanced sensitivity in sensing application. In this perspective, we develop a new photon upconversion based immunosensor for the detection of a heart failure biomarker, Brain Natriuretic Peptide (BNP) by Resonance Energy Transfer (RET) between Polyacrylic acid capped Mn2+ ions doped NaYF4:Yb/Er Upconversion Nanoparticles (PAA@Mn-NaYF4:Yb/Er UCNPs) as the donor and gold nanostar (AuNS) as the acceptor. BNP antibody was conjugated on the surface of PAA@Mn-NaYF4:Yb/Er UCNPs. The immunosensor can produce strong turn on luminescence intensity in proportional to increasing BNP antigen concentration through specific antigen–antibody interactions. The proposed photon upconversion based immunosensor can achieve turn on behaviour in the linear range from 30 pg/mL to 303 pg/mL with a Limit of Detection (LOD) of 1.76 pg/mL. The immunosensor exhibited appreciable selective and sensitive response towards BNP.

Exploring Sensitized Photon Upconversion - From Past to Present.

The conversion of low energy photons into high energy photons via triplet-triplet annihilation (TTA) photon upconversion (UC) has become a promising avenue for furthering a wide range of optoelectronic applications. Through the decades of research, many combinations of triplet sensitizer species and annihilator molecules have been investigated unlocking the entire visible spectrum upon proper pairings of sensitizer and annihilator identities. Here, we reflect upon the seminal works which lay the foundation for TTA-UC originating from solution-based methods and highlight the recent advances made within the solid state primarily focusing on perovskite-based triplet generation.

Correction to the quantum relation of photons in the Doppler effect based on a special Lorentz violation model

The possibility of the breaking of Lorentz symmetry has been discussed in many models of quantum gravity. In this paper we follow the Lorentz violation model in Ref. [14] (i.e., our previous work) to discuss the Doppler frequency shift of photons and the Compton scattering process between photons and electrons, pointing out that following the idea in Ref. [14] we have to modify the usual quantum relation of photons in the Doppler effect. But due to the current limited information and knowledge, we could not yet determine the specific expression for the correction coefficient in the modified quantum relation of photons. However, the phenomenon called spontaneous radiation in a cyclotron maser give us an opportunity to see what the expression for this correction coefficient might look like. Therefor, under some necessary constraints, we construct a very concise expression for this correction coefficient through the discussion of different cases. And then we use this expression to analyze the wavelength of radiation in the cyclotron maser, which tends to a limited value at v → c, rather than to 0 as predicted by the Lorentz model. And the inverse Compton scattering phenomenon is also discussed and we find that there is a limit to the maximum energy that can be obtained by photons in the collision between extremely relativistic particles and low-energy photons, which conclusion is also very different from that obtained from the Lorentz model, in which the energy that can be obtained by the photon tends to be infinite as the velocity of particle is close to c. This paper still follows the purpose in Ref. [14] that the energy and momentum of particles (i.e., any particles, including photons) cannot be infinite, otherwise it will make some physical scenarios invalid. When the parameter Q characterizing the degree of deviation from the Lorentz model is equal to 0, all the results and conclusions in this paper will return to the case as in the Lorentz model, so this paper also provides us with a possible experimental scheme to determine the value of Q in Ref. [14], although it still requires extremely high experimental energy.