Threshold Energy Research Articles

The eXact integral simplified time-dependent density functional theory (XsTD-DFT).

In the framework of simplified quantum chemistry methods, we introduce the eXact integral simplified time-dependent density functional theory (XsTD-DFT). This method is based on the simplified time-dependent density functional theory (sTD-DFT), where all semi-empirical two-electron integrals are replaced by exact one- and two-center two-electron integrals, while other approximations from sTD-DFT are kept. The performance of this new parameter-free XsTD-DFT method was benchmarked on excited state and (non)linear response properties, including ultra-violet/visible absorption, first hyperpolarizability, and two-photon absorption (2PA). For a set of 77 molecules, the results from the XsTDA approach were compared to the TDA data. XsTDA/B3LYP excitation energies only deviate on average by 0.14eV from TDA while drastically cutting computational costs by a factor of 20 or more depending on the energy threshold chosen. The absolute deviations of excitation energies with respect to the full scheme are decreasing with increasing system size, showing the suitability of XsTDA/XsTD-DFT to treat large systems. Comparing XsTDA and its predecessor sTDA, the new scheme generally improves excitation energies and oscillator strengths, in particular, for charge transfer states. TD-DFT first hyperpolarizability frequency dispersions for a set of push-pull π-conjugated molecules are faithfully reproduced by XsTD-DFT, while the previous sTD-DFT method provides redshifted resonance energy positions. Excellent performance with respect to the experiment is observed for the 2PA spectrum of the enhanced green fluorescent protein. The obtained robust accuracy similar to TD-DFT at a fraction of the computational cost opens the way for a plethora of applications for large systems and in high throughput screening studies.

Ultra-low threshold deep ultraviolet generation in a hollow-core fiber.

Tunable ultrashort pulses in the ultraviolet spectral region are in great demand for a wide range of applications, including spectroscopy and pump-probe experiments. While laser sources capable of producing such pulses exist, they are typically very complex. Notably, resonant dispersive-wave (RDW) emission has emerged as a simple technique for generating such pulses. However, the required pulse energy used to drive the RDW emission, so far, is mostly at the microjoule level, requiring complicated and expensive pump sources. Here, we present our work on lowering the pump energy threshold for generating tuneable deep ultraviolet pulses to the level of tens of nanojoules. We fabricated a record small-core antiresonant fiber with a hollow-core diameter of just 6 μm. When filled with argon, the small mode area enables higher-order soliton propagation and deep ultraviolet (220 to 270 nm) RDW emission from 36 fs pump pulses at 515 nm with the lowest pump energy reported to date (tens of nanojoules). This approach will allow the use of low-cost and compact laser oscillators to drive nonlinear optics in gas-filled fibers for the first time to our knowledge.

Assessing tissue differentiation capabilities in X-ray imaging through cadmium zinc telluride (CZT) photon counting detectors.

In recent years, the use of photon-counting detection technology has resulted in significant X-ray imaging research. This advanced technology holds considerable promise for enhancing Computed Tomography (CT) scanners, offering a potential solution to the limitations inherent in traditional CT detectors. The ongoing studies are dedicated to assessing the effectiveness and sensitivity of semiconductor detector materials in photon counting detectors, particularly in their ability to detect soft tissue contrasts. This study aimed to characterize the performance of the Cadmium Zinc Telluride (CZT) photon counting detector in identifying various tissues with a focus on assessing its sensitivity in distinguishing tissue types in X-ray imaging. An optimal frame rate per second (FPS) of the CZT detector was evaluated by setting the X-ray tube voltage and current at 25 keV and 35 keV and 0.5 mA, 1.0 mA respectively. By keeping the optimum FPS fixed, the detector energy thresholds were set in small steps from 15 keV to 35 keV and the tube currents were set for X-ray tubes in ranges of 0.1 mA–1.0 mA to evaluate the relationship between voltage and current of the X-ray source and counts per second (CPS). The specimens, including fat, liver, muscles, paraffin wax, and contrast media were placed on a stair-step chamber constructed from Plexi-glass, spanning six distinct thickness levels. We investigated X-ray transmission across these tissue samples at varying thicknesses, exploring five energy thresholds: 21 keV, 25 keV, 29 keV, 31 keV, and 45 keV to evaluate their impact on the CPS. This study found that a frame rate of 12 frames per second optimally aligns with the spectral response of the X-ray source. Furthermore, a linear correlation is present between the CPS and the X-ray tube current. The transmission of X-rays through a sample depends on its thickness, a phenomenon observed across different energy thresholds in this study. The detectors exhibit high sensitivity and linearity, ensuring accurate and reliable measurements in diverse imaging scenarios, making them invaluable tools for precise data acquisition in both research and clinical applications.

Standardizing technical parameters and terms for abdominopelvic photon-counting CT: laying the groundwork for innovation and evidence sharing.

Photon-counting detector CT (PCD-CT) is a new technology that has multiple diagnostic benefits including increased spatial resolution, iodine signal, and radiation dose efficiency, as well as multi-energy imaging capability, but which also has unique challenges in abdominal imaging. The purpose of this work is to summarize key features, technical parameters, and terms, which are common amongst current abdominopelvic PCD-CT systems and to propose standardized terminology (where none exists). In addition, user-selectable protocol parameters are highlighted to facilitate both scientific evaluation and early clinical adoption. Unique features of PCD-CT systems include photon-counting detectors themselves, energy thresholds and bins, and tube potential considerations for preserved spectral separation. Key parameters for describing different PCD-CT systems are reviewed and explained. While PCD-CT can generate multi-energy images like dual-energy CT, there are new types of images such as threshold images, energy bin images, and special spectral images. The standardized terms and concepts herein build upon prior interdisciplinary consensus and have been endorsed by the newly created Society of Abdominal Radiology Photon-counting CT Emerging Technology Commission.

Mn2+ Mediated Spin‐Exchange Enables CsPbBr3 Nanoplatelets to Function as Highly Efficient Triplet Sensitizers for Triplet‐Triplet Annihilation Upconversion

AbstractPerovskite nanoplatelets (NPls) have emerged as a new generation of nanomaterials that are promising for optoelectronic applications due to their large absorption and fast yet efficient emission. Particularly, they are also potential triplet sensitizers for triplet‐triplet annihilation upconversion (TTA‐UC), provided that the fast intrinsic decay of exciton can be circumvented. Herein, doping the CsPbBr3 NPls with Mn2+ (Mn2+: CsPbBr3 NPls) can efficiently convert fast‐decay triplet exciton to a long‐lived excited state of Mn2+ through Dexter‐type spin‐allowed energy transfer, enabling simultaneous large absorption and long‐lived excited state are demonstrated. Additionally, similar to the exciton‐to‐Mn2+ energy transfer, Mn2+‐to‐triplet state of annihilator energy transfer is also spin‐allowed and thus highly efficient. These pave the way for using Mn2+: CsPbBr3 NPls as triplet sensitizers. The superior triplet sensitization ability of Mn2+: CsPbBr3 NPls is demonstrated by using 9,10‐diphenylanthracene molecules (DPA) as representative annihilators. 93% quenching of Mn2+ emission and considerably accelerated decay of Mn2+ are observed after the addition of a trace amount of DPA. TTA‐UC measurement demonstrates that benefitted from the long‐lived excited state of Mn2+, the normalized upconversion photoluminescence quantum yield is ≈10% with an energy threshold being as low as ≈0.35 W cm−2. The results shed new light on using Mn2+: CsPbBr3 NPls as a triplet sensitizer.

The effects of intra-detector Compton scatter on low-frequency DQE for photon-counting CT using edge-on-irradiated silicon detectors.

Edge-on-irradiated silicon detectors are currently being investigated for use in full-body photon-counting computed tomography (CT) applications. The low atomic number of silicon leads to a significant number of incident photons being Compton scattered in the detector, depositing a part of their energy and potentially being counted multiple times. Even though the physics of Compton scatter is well established, the effects of Compton interactions in the detector on image quality for an edge-on-irradiated silicon detector have still not been thoroughlyinvestigated. To investigate and explain effects of Compton scatter on low-frequency detective quantum efficiency (DQE) for photon-counting CT using edge-on-irradiated silicondetectors. We extend an existing Monte Carlo model of an edge-on-irradiated silicon detector with 60mm active absorption depth, previously used to evaluate spatial-frequency-based performance, to develop projection and image domain performance metrics for pure density and pure spectral imaging tasks with 30and 40cm water backgrounds. We show that the lowest energy threshold of the detector can be used as an effective discriminator of primary counts and cross-talk caused by Compton scatter. We study the developed metrics as functions of the lowest threshold energy for root-mean-square electronic noise levels of 0.8, 1.6, and 3.2keV, where the intermediate level 1.6keV corresponds to the noise level previously measured on a single sensor element in isolation. We also compare the performance of a modeled detector with 8, 4, and 2 optimized energy bins to a detector with 1-keV-widebins. In terms of low-frequency DQE for density imaging, there is a tradeoff between using a threshold low enough to capture Compton interactions and avoiding electronic noise counts. For 30cm water phantom, 4 energy bins, and a root-mean-square electronic noise of 0.8, 1.6, and 3.2keV, it is optimal to put the lowest energy threshold at 3, 6, and 1keV, which gives optimal projection-domain DQEs of 0.64, 0.59, and 0.52, respectively. Low-frequency DQE for spectral imaging also benefits from measuring Compton interactions with respective optimal thresholds of 12, 12, and 13keV. No large dependence on background thickness was observed. For the intermediate noise level (1.6keV), increasing the lowest threshold from 5 to 35keV increases the variance in a iodine basis image by 60%-62% (30cm phantom) and 67%-69% (40cm phantom), with 8 bins. Both spectral and density DQE are adversely affected by increasing the electronic noise level. Image-domain DQE exhibits similar qualitative behavior as projection-domainDQE. Compton interactions contribute significantly to the density imaging performance of edge-on-irradiated silicon detectors. With the studied detector topology, the benefit of counting primary Compton interactions outweighs the penalty of multiple counting at all lowest threshold energies. Compton interactions also contribute significantly to the spectral imaging performance for measured energies above10keV.

Femtosecond Laser Nanomachining of High‐Aspect‐Ratio Channels in Bulk Fused Silica

AbstractThee‐dimensional nano‐structuring of bulk fused silica glass remains a challenging issue due to limitations of traditional fabrication methods. In the present work the fabrication of hollow mm‐length channels is demonstrated in bulk fused silica by femtosecond laser irradiation followed by chemical etching, achieving feature sizes of 300 nm. The tight focusing and threshold energy conditions allow to reveal unexplored fabrication regimes. The robustness and repeatability of the process are demonstrated through the fabrication of fused silica diffraction gratings, made of parallel hollow channels with variable pitches even in the sub‐wavelength regime.

Investigation of Electronic and Molecular Features of Zn3S3/PEG4000 Nano-Composite Using the DFT Method

Molecular geometry structures were accurately optimized to low convergence energy thresholds for the Zn3S3 cluster before and after adding Polyethylene Glycol (PEG4000). Density functional theory DFT/ B3LYP calculations with 6-113G (d, p) basis set were employed to investigate structural and electronic properties of Zn3S3/PEG4000 composite. The FTIR spectral lines were analyzed where an agreement of FTIR spectra of titled molecules was evaluated between experimental and theoretical findings of the active peaks of O–H, C–H, C=O, C–O–C, and Zn–S functional groups. The vibrational modes frequencies were systematically analyzed on the distribution basis of potential energy around the range 0–4000 cm-1 and observed 12 modes of vibrations for the Zn3S3 molecule, while 36 modes for the Zn3S3/PEG4000 compound. Frontier high occupied, and low unoccupied molecular orbitals (HOMO&LUMO) were calculated and plotted to obtain the energy gap (E𝒈) resulting from the difference between those orbitals. The promising indicator was obtained at increasing E𝒈 from (4.031 to 4.459) eV after adding PEG4000, pointing out the effect of polymer on the ZnS surface as a capping agent. Additionally, electronic features of the mentioned structures, such as IP, EA, Ef, E𝒈, 𝐶𝑝, χ, η, Ѕ, and ω, were calculated. Finally, the molecular electrostatic potential (MEP) diagram of Zn3S3 and Zn3S3/ PEG4000 and charge densities of isosurface and contour diagrams were estimated, showing the nucleophilic and electrophilic attack of these compounds.

Improvements in charged lepton and photon propagation for the software PROPOSAL

Accurate particle simulations are essential for the next generation of experiments in astroparticle physics. The Monte Carlo simulation library PROPOSAL is a flexible tool to efficiently propagate high-energy leptons and photons through large volumes of media, for example in the context of underground observatories. It is written as a C++ library, including a Python interface. In this paper, the most recent updates of PROPOSAL are described, including the addition of electron, positron, and photon propagation, for which new interaction types have been implemented. This allows the usage of PROPOSAL to simulate electromagnetic particle cascades, for example in the context of air shower simulations. The precision of the propagation has been improved by including rare interaction processes, new photonuclear parametrizations, deflections in stochastic interactions, and the possibility of propagating in inhomogeneous density distributions. Additional technical improvements regarding the interpolation routine and the propagation algorithm are described. New version program summaryProgram Title: PROPOSAL.CPC Library link to program files:https://doi.org/10.17632/g478pjdcxy.2.Developer's repository link:https://github.com/tudo-astroparticlephysics/PROPOSAL.Licensing provisions: LGPL.Programming language: C++, Python.Journal reference of previous version: Comput. Phys. Commun. 242 (2019) 132.Does the new version supersede the previous version?: Yes.Reasons for the new version: Substantial addition of features. Various bugfixes.Summary of revisions: The library now also treats photons and has the corresponding processes implemented. New parametrizations for photonuclear interaction have been implemented. The angular deflection in stochastic energy losses has been implemented in addition to the already existing multiple scattering implementation, which has been improved to reduce the runtime. The implementation of the Landau-Pomeranchuk-Migdal effect has been corrected. The propagation algorithm has been improved, including the support of inhomogeneous density distributions.Nature of problem: Three-dimensional propagation of charged leptons and photons through different media. Particles lose energy stochastically by ionization, bremsstrahlung, pair production, and photonuclear interaction for charged leptons (including annihilation with atomic electrons for positrons) and Compton scattering, pair production, photoelectric effect and photohadronic interaction for photons. Additionally, they are deflected while propagating through the medium due to both multiple elastic Coulomb scattering as well as deflections in individual stochastic interactions. Unstable particles eventually decay, producing secondary particles.Solution method: Monte-Carlo simulation. The library samples the next interaction point, the type of interaction process, the energy lost in this interaction process, and the energy lost until this point. Particles are propagated until they decay, lose all their kinetic energy (for photons: reach a lower energy limit defined by the validity of the underlying cross sections), or until a user-defined termination criterion is reached. For each propagation step, the angular deflection and endpoint shift due to multiple scattering is calculated.To improve the performance and deal with the divergence of the bremsstrahlung cross section for small photon energies, energy losses below a predefined relative or absolute energy threshold are treated continuously. The computation time is improved by the use of interpolation tables.

Thermodynamic signatures and phase transitions in high-energy Au–Au collision

In this study, we systematically investigate the dynamics of various hadrons namely π +, π −, K +, K −, p, p¯ , Λ, Λ¯ , Ξ− and Ξ¯+ produced in central Au–Au collisions. We analyze data of AGS and RHIC, which span a broad range of collision energies, ranging from sNN = 1.9 to 200 GeV. To analyze the transverse momentum (p T ) and transverse mass (m T ) distributions, we employ a two-component standard distribution function, achieving a very good representation of the experimental data across these energy regimes. We extract key thermodynamic parameters, including the effective temperature T, the mean transverse momentum 〈p T 〉, and the initial temperature T i , and analyze their dependence on the values of collision energy and particle mass. Our findings reveal a distinct transition behaviour around sNN=19.6GeV . Below sNN=19.6GeV , the values of T, 〈p T 〉, and T i increase monotonically for all hadrons due to higher energy transfer into the system. Above this energy threshold, these extracted parameters plateau, suggesting that the additional energy is utilized as latent heat for phase transition rather than increasing the system’s temperature. These observations delineate two distinct regions: a hadron-dominated region at lower energies and a parton-dominated region at higher energies, each potentially indicative of different phases of matter, with the latter possibly signalling the onset of a quark–gluon plasma. The study thus provides critical insights into the complex interplay of thermodynamics, phase transitions, and particle interactions in high-energy Au–Au collisions.

Kinetic energy dependence and potential energy surface of the spin-forbidden reaction Sm+ (8F) + N2O (1Σ+) → SmO+ (6Δ) + N2 (1Σg+).

The kinetic energy dependence of the title reaction is examined using guided ion beam tandem mass spectrometry. Because this reaction is spin-forbidden, crossings between octet and sextet hypersurfaces presumably must occur. Furthermore, Sm+ must transition from a 4f66s1 configuration in the reactant to 4f55d2 in order to have the orbital occupancy required to form the triple bond in SmO+ (6Δ). Despite being strongly exothermic (∼4eV), the reaction proceeds with low efficiency (18% ± 4%) via a barrierless process at low energies. Below ∼0.3eV, the cross section follows a kinetic energy dependence that roughly parallels that of the collision rate for ion-dipole reactions. At higher collision energies, the reaction cross section increases until it follows the trajectory cross section closely from 3 to 5eV, indicating that another pathway opens on the reaction hypersurface. Modeling this increase yields a threshold energy for this new pathway at 0.54 ± 0.05eV. Theoretical potential energy surfaces that do not include spin-orbit interactions for the reaction show that there is a barrier of height 1.19eV (MP2) or 0.49eV [CCSD(T)] to insertion of Sm+ into the N2-O bond and that there are several places where octet and sextet surfaces can intersect and interact. By considering the distribution of spin-orbit states generated in the ion source, the internal energy of the N2O reactant, and the influence of coupling between electronic, orbital, and rotational angular momentum, the low-efficiency, exothermic behavior as well as the increase in efficiency at higher energies can plausibly be explained.

Crystallization-driven tuneable lasing of perylene doped into the nematic liquid crystal

Versatile devices with tunable capabilities for controlling lasing wavelength and intensity are in high demand. Liquid crystals (LCs) exhibit immense potential for such applications, offering fine-tuning possibilities through external factors. On the other hand, laser technology is currently a research hotspot in optoelectronics, and also in practical applications. The recent market introduction of laser television marks a significant stride toward making such advanced technology accessible in every household. In synergy with laser pumping, the LCs unquestionably can be rediscovered. This study presents a comprehensive investigation into the crystallization phenomenon within a host-guest device, compact in size, free from moving parts, and integrating the liquid crystalline (LC) matrix doped with 3,4,9,10-tetra-(3-alcoxy-carbonyl)-perylene (THCP) dye. The focus lies in examining the influence of varying dye concentrations on multicolor fluorescence, lasing behavior, and device morphology. The systematic analysis of Random Lasing (RL) energy thresholds and the impact of DC voltage on light intensity modulation is demonstrated. Morphological changes were monitored in real-time using optical microscopy techniques, including crossed polarizer, and fluorescence imaging under 450 nm excitation. Utilizing advanced Transmission Electron Microscopy (TEM) techniques, we explore exceptional insights into our set of devices, providing novel information about the THCP crystallization process for the first time in the literature. To gain a comprehensive understanding of the crystal forming and molecular geometry we examined additionally the THCP dye, using X-ray diffraction and Raman spectroscopy. Furthermore, we showcase that varying the pumping energy enables multicolor tuning in the fabricated systems, presenting an attractive feature in the context of laser display technologies.

Deuteron breakup effects on the d + 12C, 15N, 16O, 24Mg, 32S, 58Ni, and 70Ge elastic scattering angular distributions

Motivated by the well-known n + p cluster structure of deuterons, which appears at breakup threshold energy of 2.225 MeV, the angular distributions (ADs) for elastically scattered deuterons from various targets, namely, 12C, 15N, 16O, 24Mg, 32S, 58Ni, and 70Ge at different energies, are investigated microscopically within the continuum discretized coupled channel (CDCC) method as well as an effective potential (Ueff), considered as the sum of cluster folding and dynamical polarization potentials. The Ueff potentials were employed successfully to reproduce the elastic ADs data for the considered systems in a wide range of energies. The investigation gives evidence for the applicability of the Ueff in describing the ADs data for many nuclear systems.

Comparison of residual dose rates from MARS and DORIAN simulations with experimental data from the SINBAD database

This benchmarking study aims to compare residual dose rate predictions from the MARS and DORIAN codes with experimental measurements taken from samples irradiated at CERN's CERF facility. The research evaluates the residual dose rates of these samples over varied cooling intervals. Additionally, it delves into the influence of parameter choices, such as specific physics processes and energy thresholds, on the production and transport of particles and their effects on simulation outcomes. While both MARS and DORIAN largely align with experimental findings, discrepancies were observed in the copper sample. This prompted an in-depth examination of the elevated dose rates from MARS.

The Formation and Transformation of Low-Dimensional Carbon Nanomaterials by Electron Irradiation.

Low-dimensional materials based on graphene or graphite show a large variety of phenomena when they are subjected to irradiation with energetic electrons. Since the 1990s, electron microscopy studies, where a certain irradiation dose is unavoidable, have witnessed unexpected structural transformations of graphitic nanoparticles. It is recognized that electron irradiation is not only detrimental but also bears considerable potential in the formation of new graphitic structures. With the availability of aberration-corrected electron microscopes and the discovery of techniques to produce monolayers of graphene, detailed insight into the atomic processes occurring during electron irradiation became possible. Threshold energies for atom displacements are determined and models of different types of lattice vacancies are confirmed experimentally. However, experimental evidence for the configuration of interstitial atoms in graphite or adatoms on graphene remained indirect, and the understanding of defect dynamics still depends on theoretical concepts. This article reviews irradiation phenomena in graphene- or graphite-based nanomaterials from the scale of single atoms to tens of nanometers. Observations from the 1990s can now be explained on the basis of new results. The evolution of the understanding during three decades of research is presented, and the remaining problems are pointed out.

Experimental investigation on the effects of stainless-steel mesh reinforcing layers on low-velocity impact response of hybrid thermoplastic glass fiber composites

This study aims to assess the hybridization effect on the perforation threshold of Low-Velocity Impact (LVI) in thermoplastic glass composite laminates, incorporating layers of resin-impregnated stainless-steel mesh. Reinforcing methodologies such as hybridization are recently being adopted as a practical approach to increasing the energy-absorbing capacity of polymer composites. In the current paper, a multi-step hot press lamination method has been employed to fabricate the hybrid composite laminates strengthened with stainless-steel mesh layers. Several stacking sequences, metal mesh wire sizes, orientation and position relative to the impactor have been examined under various LVI energies. It was revealed that the LVI penetration energy was increased for the thermoplastic-based composite laminates reinforced with stainless-steel mesh layers. Furthermore, the LVI penetration energy threshold was significantly influenced by the metal mesh wire size, orientation and stacking sequence. Finally, the backlight method capability was assessed to detect the after-impact interlaminar damages.

Radiation tolerance test and performance verification of pnCCD at high temperatures for future satellite mission HiZ-GUNDAM

A wide-field X-ray survey in the soft X-ray band is crucial for future satellite missions in the astronomical observations. HiZ-GUNDAM, currently under development, is a proposed satellite designed to observe soft X-ray transients including gamma-ray bursts. This satellite employs wide-field X-ray monitors consisting of lobster-eye optics and focal-plane pixel sensors in the soft X-ray band of 0.4–4 keV. A pnCCD is a candidate for focal-plane Si pixel detectors, featuring a back-illuminated X-ray CCD, large pixel size (70–100 µm), and a large active image area of approximately 55 × 55 mm2 for the flight model. Here, we investigated the basic characteristics and performance of the small-size pnCCD with 128 × 256 pixels, a pixel size of 75 µm, and a detector thickness of 450 µm. High-energy cosmic rays such as protons can degrade the performance of pnCCDs by increasing dark current and charge transfer inefficiency due to ionizing and displacement damage. These factors may affect soft X-ray observations, potentially causing the degradation of lower-detectable energy thresholds and an increase in the number of hot pixels. Therefore, we conducted a radiation tolerance test at room temperature using a proton beam. After irradiating the pnCCD with 10-MeV protons equivalent to three years of nominal operation for HiZ-GUNDAM, we found that the operation temperatures of the pnCCD should be lower than -35 °C. This requirement will be incorporated into the design of the mission operation system.

Transmission in graphene through a double laser barrier

We study the tunneling behavior of Dirac fermions in graphene subjected to a double barrier potential profile created by spatially overlapping laser fields. By modulating the graphene sheet with an oscillating structure formed from two laser barriers, we aim to understand how the transmission of Dirac fermions is influenced by such a light-induced electric potential landscape. Using the Floquet method, we determine the eigenspinors of the five regions defined by the barriers applied to the graphene sheet. Applying the continuity of the eigenspinors at barrier edges and using the transfer matrix method, we establish the transmission coefficients. These allow us to show that oscillating laser fields generate multiple transmission modes, including zero-photon transmission aligned with the central band ε and photon-assisted transmission at sidebands ε + l ϖ, with l = 0, ± 1, ⋯ and frequency ϖ. For numerical purposes, our attention is specifically directed towards transmissions related to zero-photon processes (l = 0), along with processes involving photon emission (l = 1) and absorption (l = − 1). We find that transmission occurs only when the incident energy is above the threshold energy ε > k y + 2ϖ, with transverse wave vector k y . We find that the variation in distance d 1 separating two barriers of widths d 2 − d 1 suppresses one transmission mode. Additionally, we show that an increase in laser intensity modifies transmission sharpness and amplitude.

Searching for WIMPs with TREX-DM: achievements and challenges

The TREX-DM detector, a low background chamber with microbulk Micromegas readout, was commissioned in the Canfranc Underground Laboratory (LSC) in 2018. Since then, data taking campaigns have been carried out with argon and neon mixtures, at different pressures from 1 to 4 bar. By achieving a low energy threshold of 1 keV ee and a background level of 80 counts keV-1 kg-1 day-1 in the region from 1 to 7 keV ee , the experiment demonstrates its potential to search for low-mass WIMPs. Two of the most important challenges currently faced are the reduction of both, background level and energy threshold. With respect to the energy threshold, recently a new readout plane is being developed, based on the combination of Micromegas and GEM technologies, aiming to have a pre-amplification stage that would permit very low energy thresholds, close to the single-electron ionization energy. With respect to the background reduction, apart from studies to identify and minimize contamination population, a high sensitivity alpha detector is being developed in order to allow a proper material selection for the TREX-DM detector components. Both challenges, together with the optimization of the gas mixture used as target for the WIMP detection, will take TREX-DM to explore regions of WIMP's mass below 1 GeV c -2.

Study the Cross Section of 67Ga(n,p)67Zn Reaction by using the Revers Reaction in the Ground State

In this study the excitation function for 67Ga(n,p)67Zn nuclear reaction in the ground state has been calculated using the reciprocity theorem. The decay energy of proton particles equal to (-1.78369) MeV according to the available International Atomic Energy Agency (IAEA) for 67Zn (p,n) 67Ga nuclear reaction with threshold energy (1.81054 MeV) and this data replicated in fine proceedings for specified energy range. The cross-section calculations in a present work shows same behavior of the corresponding experimental data and with previous theoretical work using statistical model.