Narrow Energy Range Research Articles

First-principles calculations for transient absorption of laser-excited magnetic materials

We investigate the modification in the optical properties of laser-excited bulk cobalt and nickel using the time-dependent density functional theory at a finite electron temperature. As a result of the first-principles simulation, a complex change in the photoabsorption of the magnetic materials is observed around the M 2,3 absorption edge. Based on the microscopic analysis, we clarify that this complex absorption change consists of the two following components: (i) the decrease in the photoabsorption in a narrow energy range around the M 2,3 edge, which reflects the blue shift of the absorption edge due to the light-induced demagnetization, and (ii) the increase in the photoabsorption in a wider range around the M 2,3 edge, which reflects the modification in the local-field effect due to the light-induced electron localization. The relation between the transient optical and magnetic properties may open a way to monitor ultrafast (de)magnetization and spin dynamics in magnetic materials via transient absorption spectroscopy.

Deterministic and Scalable Generation of Exciton Emitters in 2D Semiconductor Nanodisks

AbstractIn recent cryogenic measurements, narrow photoluminescence (PL) peaks due to diverse quantum emitters have been found at random locations of monolayer transition metal dichalcogenides (TMDs), which impedes precise optoelectronic applications. Thus, it is of great importance to truly regulate these localized exciton emissions by deterministic spatial and spectral control. Here, such desired emission is primarily demonstrated in monolayer WS2 nanodisks. The size‐dependent PL studies indicate the clear evolution from the broad defect‐band emission to a set of spectrally isolated narrow peaks (linewidth of ≈ sub nm) at 4.2 K, which is associated with the prevailing effect of edge defects with the shrinkage of the disk diameter, providing a narrow emission energy range for bound excitons. When the disk diameter is reduced to 300 nm, more than 80% of emitter peaks are located between 610 and 616 nm, verifying the effective control of emission wavelength of these photon emitters. Furthermore, the strategy is extended to prepare scalable WS2 nanodisk arrays based on flakes of hundreds of µm, and size‐dependent narrow emissions of WSe2 nanodisks are testified. This work develops a defect‐engineering strategy to generate localized exciton emitters toward the promising TMD‐based optoelectronic applications.

СРАВНЕНИЕ ОСНОВНЫХ ЧАСТОТНО-ВРЕМЕННЫХ ПРЕОБРАЗОВАНИЙ СПЕКТРАЛЬНОГО АНАЛИЗА СИГНАЛОВ АКУСТИЧЕСКОЙ ЭМИССИИ

Due to the intensive development of spectroscopic techniques for detecting acoustic emission signals, the problem of providing the best time-frequency resolution through the application of specific time-frequency transformation algorithms comes to the fore. The Short-Time Fourier Transform, the Wavelet Transform, the Smoothed Pseudo Wigner Distribution, the Choi-Williams Distribution, and the Hilbert-Huang Transform are currently the main time-frequency transformations used or integrated into the acoustic emission method. However, today in the literature, there is not enough information that allows evaluating time-frequency transformations regarding the effectiveness of their application to specify the features of discrete and continuous acoustic emission signals. On this basis, the authors carried out an experimental comparison of synthetic and actual model signals to determine the efficiency of specified time-frequency transformations. The synthetic model signals were a chirp signal, ideal sinusoids, and a Dirac delta function. The actual signals were a discrete acoustic emission signal from the Hsu Nelson source decomposed into dispersion modes in the acoustic channel and a continuous acoustic emission signal from the air outflow through a calibrated hole. The analysis shows that only the Fourier transform and the Wavelet transform can define all control features of model signals at the frequency components’ energy gap of about 25 dB. Wigner Distribution, Choi-Williams Distribution, and Hilbert-Huang Transform demonstrated higher time-frequency resolution did not identify frequency components of low energy. Therefore, the authors recommend using them to identify spectral changes in the resonance and discrete signals but in the narrow energy range. The Fourier transform and the Wavelet transform demonstrated the best result to analyze continuous acoustic emission. However, to use the latter, the procedure of selection of the optimal basis function is necessary. The study determined that the Hilbert-Huang transform allows identifying the frequency fluctuations, but it is necessary to develop ways to increase sensitivity and extract basic information from the spectrograms to enhance the validity of its results.

X-Ray Emission of the γ-ray-loud Young Radio Galaxy NGC 3894

Abstract The radio source 1146+596 is hosted by the elliptical/S0 galaxy NGC 3894, with a low-luminosity active nucleus. The radio structure is compact, suggesting a very young age for the jets in the system. Recently, the source has been confirmed as a high-energy (HE; >0.1 GeV) γ-ray emitter in the most recent accumulation of Fermi Large Area Telescope data. Here we report on the analysis of the archival Chandra X-ray Observatory data for the central part of the galaxy, consisting of a single 40 ks long exposure. We have found that the core spectrum is best fitted by a combination of an ionized thermal plasma with a temperature of ≃0.8 keV, and a moderately absorbed power-law component (photon index Γ = 1.4 ± 0.4, hydrogen column density N H/1022 cm−2 = 2.4 ± 0.7). We have also detected the iron Kα line at 6.5 ± 0.1 keV, with a large equivalent width of 1.0 − 0.5 + 0.9 keV. Based on the simulations of Chandra's point-spread function, we have concluded that while the soft thermal component is extended on the scale of the galaxy host, the hard X-ray emission within the narrow photon energy range 6.0–7.0 keV originates within the unresolved core (effectively the central kiloparsec radius). The line is therefore indicative of the X-ray reflection from a cold neutral gas in the central regions of NGC 3894. We discuss the implications of our findings in the context of the X-ray Baldwin effect. NGC 3894 is the first young radio galaxy detected in HE γ-rays with the iron Kα line.

Comparative studies of C7H10N2 pyridine and C7H10N2S pyrrole for optoelectronic applications by mBJ approach.

The modified Becke-Johnson exchange (mBJ) potential plus the generalized gradient approximation (GGA) correlation are used for the calculation of the optoelectronic properties of the C7H10N2 pyridine and C7H10N2S pyrrole. Electronic band gaps of C7H10N2 pyridine and C7H10N2S pyrrole have been determined to be 4.65eV and 3.41eV by band structure spectra, respectively. According to the Penn model, there is an inverse relationship between the band gap value and static dielectric constant along the x-direction. The density of states spectra shows that the p state of S atoms plays a key role in the optical spectra. In the refractive index spectra, the nature of materials changes from linear to nonlinear with superluminal nature in a narrow energy range of 3.9-4.7eV for C7H10N2S and 5-7.7eV for C7H10N2. Cauchy parameters are calculated and predicted values are extended in the UV (ultraviolet) and visible regions. Obtained plasmon energies are in close agreement with suitable optical materials such as α-Al2O3 making the material more effective to use in new optical devices.

Correlating chemical and electronic states from quantitative photoemission electron microscopy of transition-metal dichalcogenide heterostructures

Vertical heterostructures of MoS2 and WSe2 layers are studied by spectroscopic photoemission electron microscopy as an effective technique for correlating chemical and electronic states at the micrometer scale. Element-specific, surface-sensitive images recorded at high lateral and energy resolution from core-level photoelectrons using different laboratory excitation sources are postprocessed to obtain laterally resolved maps of elemental composition and energy shifts in the Mo3d spectra of a few hundred meV. For monolayer MoS2, the method reveals substrate-dependent charge transfer properties within the narrow energy range of 360 meV, with MoS2 becoming more n-type after transfer onto WSe2. The band structure data from momentum microscopy taken over the same areas confirm the charge transfer from WSe2 to MoS2 by the shift of the K-bands away from the Fermi level and illustrates the layer-specific contributions to the electronic band structure of the heterostructure. From work function mapping, the reconstructed energy-level diagram reveals a type II heterostructure but with a very small conduction-band offset.

Superior room-temperature power factor in GeTe systems via multiple valence band convergence to a narrow energy range

GeTe systems are excellent p-type thermoelectric materials at medium temperatures (500–800 K). Recently, their electronic properties were enhanced by band convergence of L and Σ valence bands, which increased the power factor at 500–800 K. However, there are only a few thermoelectric materials suitable for lower-temperature waste-heat recovery applications, and their demand is rapidly increasing. Herein, we demonstrated that the well-known L and Σ bands of GeTe and the additional Δ band converge at a desirable energy level to a very narrow energy range as a result of fine-tuning the crystal symmetry and composition by forming a GeTe-Sb2Te3 alloy. Alloying additionally facilitates a decrease in the bandgap, thereby increasing the near-room-temperature power factor. The GeTe-Sb2Te3 alloy achieved very high room-temperature and maximum power factors of 2.6 mW m−1 K−2 at 300 K and 3.3 mW m−1 K−2 at 423 K, respectively, despite GeTe being a medium-temperature thermoelectric material. Thus, we confirmed the applicability of GeTe as a thermoelectric material at room temperature. This study facilitates the development of high-performance near-room-temperature thermoelectric materials based on existing medium-temperature systems.

Achieving two-dimensional optical spectroscopy with temporal and spectral resolution using quantum entangled three photons.

Recent advances in techniques for generating quantum light have stimulated research on novel spectroscopic measurements using quantum entangled photons. One such spectroscopy technique utilizes non-classical correlations among entangled photons to enable measurements with enhanced sensitivity and selectivity. Here, we investigate the spectroscopic measurement utilizing entangled three photons. In this measurement, time-resolved entangled photon spectroscopy with monochromatic pumping [A. Ishizaki, J. Chem. Phys. 153, 051102 (2020)] is integrated with the frequency-dispersed two-photon counting technique, which suppresses undesired accidental photon counts in the detector and thus allows one to separate the weak desired signal. This time-resolved frequency-dispersed two-photon counting signal, which is a function of two frequencies, is shown to provide the same information as that of coherent two-dimensional optical spectra. The spectral distribution of the phase-matching function works as a frequency filter to selectively resolve a specific region of the two-dimensional spectra, whereas the excited-state dynamics under investigation are temporally resolved in the time region longer than the entanglement time. The signal is not subject to Fourier limitations on the joint temporal and spectral resolution, and therefore, it is expected to be useful for investigating complex molecular systems in which multiple electronic states are present within a narrow energy range.

Anharmonic phonons and anomalous thermal expansion of graphite

We have investigated the anisotropic thermal expansion of graphite using ab-initio calculations of the implicit and explicit anharmonicity of phonons, which occur due to change in volume and increase in the thermal amplitudes, respectively. We find that the negative thermal expansion (NTE) in the a-b plane below 600 K and very large positive thermal expansion along the c-axis up to high temperatures arise due to various phonons polarized along the c-axis. While the NTE arises from the anharmonicity of transverse phonons over a broad energy range up to 60 meV, the large positive expansion along the c-axis occurs largely due to the longitudinal optic phonon modes around 16 meV. We find that these phonons have large implicit anharmonicity, but very little explicit anharmonicity. We also find very significant increase in the linear compressibility along the c-axis with increase in volume, and this has important role to quantitatively explain the thermal expansion behavior along the c-axis. The hugely anisotropic bonding in graphite is found to be responsible for wide difference in the energy range of the transverse and longitudinal phonon modes polarized along the c-axis, which are responsible for the anomalous thermal expansion behavior. This behaviour is in contrast to other nearly isotropic hexagonal structures like water-ice, which show anomalous thermal expansion in a small temperature range arising from a narrow energy range of phonons.

Sustained Oxygen Spectral Gaps and Their Dynamic Evolution in the Inner Magnetosphere

AbstractVan Allen Probes observations of ion spectra often show a sustained gap within a very narrow energy range throughout the full orbit. To understand their formation mechanism, we statistically investigate the characteristics of the narrow gaps for oxygen ions and find that they are most frequently observed near the noon sector with a peak occurrence rate of over 30%. The magnetic moment (μ) of the oxygen ions in the gap shows a strong dependence on magnetic local time (MLT), with higher and lower μ values in the morning and afternoon sectors, respectively. Moreover, we find through superposed epoch analysis that the gap formation also depends on geomagnetic conditions. Those gaps formed at lower magnetic moments (μ < 3,000 keV/G) are associated with stable convection electric fields, which enable magnetospheric ions to follow a steady drift pattern that facilitates the gap formation by corotational drift resonance. On the other hand, gaps with higher μ values are statistically preceded by a gradual increase of geomagnetic activity. We suggest that ions within the gap were originally located inside the Alfven layer following closed drift paths, before they were transitioned into open drift paths as the convection electric field was enhanced. The sunward drift of these ions, with very low fluxes, forms a drainage void in the dayside magnetosphere manifested as the sustained gap in the oxygen spectrum. This scenario is supported by particle‐tracing simulations, which reproduce most of the observed characteristics and therefore provide new insights into inner magnetospheric dynamics.

Reaction kinetic, maturity, burial and thermal histories modelling of cambay shale source rocks, Cambay Basin, Western India

The Cambay Shale Formation (CSF), the known source rock for conventional oil and gas, now becomes a key target for shale oil/gas exploration in the Cambay Basin. In the present study, maturity, wellbore temperature and kerogen kinetics data from the several locations in the Cambay Basin have been integrated into PetroMod®, a basin and petroleum system modelling (BPSM) software, to generate maturity profile, burial and thermal history in the Cambay Basin. The Optkin program optimised kerogen kinetic results indicated that the activation energy for the type III kerogens, which are prominently available in the basin, varies widely (44–72 kcal/mol). A sample from Mehsana-Ahmedabad Block shows a narrow activation energy range (40–50 kcal/mol), a characteristics of type II kerogen and the maximum (91%) of the initial petroleum potential is contributed by a single activation energy (46 kcal/mol). BPSM models indicate that the major portion of the CSF in the north of the basin is mainly under early and main oil generation window, where shale oil prospect can be explored. Compared to the north part of the basin where late oil and wet gas generation windows enter into the Olpad Formation at ~2700 m and ~3100 m respectively, the source rocks, i.e. CSF at the centre of the Broach block in the South Cambay Basin indicate the presence of late oil and wet gas generation windows at ~3100 m and ~3900 m, respectively. The models generated in the study area suggest that the deeper section of the South Cambay Basin may have prospective for shale oil/gas.

Dual Modulators of Selected Plant Secondary Metabolites Targeting COVID-19 Main Protease and Interleukin-2: An In-Silico Approach based Novel Hypothesis

Background: Owing to the recent scenario on this ongoing Coronavirus pandemic outbreak around the world, the present study has been undertaken. Aim: In this study, we adopted two strategies, i.e., via computational method, a search for the novel plant secondary metabolites from the Indian Traditional Medicine to target and combat the enduring novel 2019 CoVs main protease that causes pneumonia, followed by the effect of these selected secondary metabolites on the host’s immune system for their immunomodulatory potential on Interleukin-2. Methods: A detailed literature review has been done to identify the assorted plant secondary metabolites from the natural sources, which have been extensively used traditionally for their immunomodulatory potential. Next, the resulting compounds have processed for the molecular docking study to predict whether the compounds have the potency to fight against 2019- CoVs protein or it could have the tendency to battle the cytokines, which are responsible for the immune response of the host, thereby preventing the CoVs caused infection in humans. Furthermore, to explore molecular mechanics, the insilico docking study with COVID-19 Mpro and Interleukin-2 has been performed. Results & Discussion: Among the six secondary metabolites selected, five compounds showed its possible promising potency with COVID-19 and IL-2 proteins, which are compared with the standard drug Remdesivir, one of the anti-viral drugs for treating and managing the present coronavirus condition and an IL-2 inhibitor, which is the native IL-2 ligand protein (i.e., from PDB Id- 1PW6) itself. Besides, based on the docking scores, the Curcumin (from Curcuma longa) showed the highest score towards these two targets taken for this study. The identified compounds have a promising binding affinity with the Mpro receptors, in the narrow range of binding energy for the protein PDB Id: 6LU7 and the score range between -10.9102 to -19.8790 kcal/mol: when compared to the standard -21.8600 kcal/mol. Whereas, the binding affinity with the Interleukin -2 receptor, for the protein PDB Id: 1PW6 the range between -11.3899 to -17.1366 kcal/mol: when compared to that of standard -16.9554 kcal/mol. Conclusion: Our result findings demonstrate that the integrated Indian traditional herbal treatment might be hopefully used for the viral respiratory infection due to either it may have acted directly on the viral protein or through regulating the immune response, which could lead to the rapid drug discovery of the drug leads with clinical potency towards the novel infectious disease, where there is no drug or vaccines are available.

Calibration of radiochromic EBT3 film using laser-accelerated protons

We present a proof of principle for onsite calibration of a radiochromic film (EBT3) using CR-39 as an absolute proton-counting detector and laser-accelerated protons as a calibration source. A special detector assembly composed of aluminum range filters, an EBT3 film, and a CR-39 detector is used to expose the EBT3 film with protons in an energy range of 3.65 MeV-5.85 MeV. In our design, the proton beam is divided into small beamlets and their projection images are taken on the EBT3 film and the CR-39 detector by maintaining a certain distance between the two detectors. Owing to the geometrical factor of the configuration and scattering inside the EBT3, the areal number density of protons was kept below the saturation level of the CR-39 detector. We also present a method to relate the number of protons detected on the CR-39 in a narrow energy range to protons with a broad energy spectrum that contribute to the dose deposited in the EBT3 film. The energy spectrum of protons emitted along the target normal direction is simultaneously measured using another CR-39 detector installed in a Thomson parabola spectrometer. The calibration curves for the EBT3 film were obtained in the optical density range of 0.01-0.25 for low dose values of 0.1 Gy-3.0 Gy. Our results are in good agreement with the calibrations of the EBT3 film that are traditionally carried out using conventional accelerators. The method presented here can be further extended for onsite calibration of radiochromic films of other types and for a higher range of dose values.

Raman Spectroscopy of Twisted Bilayer Graphene

When two periodic two-dimensional structures are superposed, any mismatch rotation angle between the layers generates a Moiré pattern superlattice, whose size depends on the twisting angle θ. If the layers are composed by different materials, this effect is also dependent on the lattice parameters of each layer. Moiré superlattices are commonly observed in bilayer graphene, where the mismatch angle between layers can be produced by growing twisted bilayer graphene (TBG) samples by CVD or folding the monolayer back upon itself. In TBG, it was shown that the coupling between the Dirac cones of the two layers gives rise to van Hove singularities (vHs) in the density of electronic states, whose energies vary with θ. The understanding of the behavior of electrons and their interactions with phonons in atomically thin heterostructures is crucial for the engineering of novel 2D devices. Raman spectroscopy has been often used to characterize twisted bilayer graphene and graphene heterostructures. Here, we review the main important effects in the Raman spectra of TBG discussing firstly the appearance of new peaks in the spectra associated with phonons with wavevectors within the interior of the Brillouin zone of graphene corresponding to the reciprocal unit vectors of the Moiré superlattice, and that are folded to the center of the reduced Brillouin Zone (BZ) becoming Raman active. Another important effect is the giant enhancement of G band intensity of TBG that occurs only in a narrow range of laser excitation energies and for a given twisting angle. Results show that the vHs in the density of states is not only related to the folding of the commensurate BZ, but mainly associated with the Moiré pattern that does not necessarily have a translational symmetry. Finally, we show that there are two different resonance mechanisms that activate the appearance of the extra peaks: the intralayer and interlayer electron–phonon processes, involving electrons of the same layer or from different layers, respectively. Both effects are observed for twisted bilayer graphene, but Raman spectroscopy can also be used to probe the intralayer process in any kind of graphene-based heterostructure, like in the graphene/h-BN junctions.

Data-efficient machine learning for molecular crystal structure prediction.

The combination of modern machine learning (ML) approaches with high-quality data from quantum mechanical (QM) calculations can yield models with an unrivalled accuracy/cost ratio. However, such methods are ultimately limited by the computational effort required to produce the reference data. In particular, reference calculations for periodic systems with many atoms can become prohibitively expensive for higher levels of theory. This trade-off is critical in the context of organic crystal structure prediction (CSP). Here, a data-efficient ML approach would be highly desirable, since screening a huge space of possible polymorphs in a narrow energy range requires the assessment of a large number of trial structures with high accuracy. In this contribution, we present tailored Δ-ML models that allow screening a wide range of crystal candidates while adequately describing the subtle interplay between intermolecular interactions such as H-bonding and many-body dispersion effects. This is achieved by enhancing a physics-based description of long-range interactions at the density functional tight binding (DFTB) level—for which an efficient implementation is available—with a short-range ML model trained on high-quality first-principles reference data. The presented workflow is broadly applicable to different molecular materials, without the need for a single periodic calculation at the reference level of theory. We show that this even allows the use of wavefunction methods in CSP.

The Formation of Saturn’s and Jupiter’s Electron Radiation Belts by Magnetospheric Electric Fields

Abstract The existence of planetary radiation belts with relativistic electron components means that powerful acceleration mechanisms are operating within their volume. Mechanisms that bring charged particles planetward toward stronger magnetic fields can cause their heating. On the basis that electron fluxes in Saturn’s radiation belts are enhanced over discrete energy intervals, previous studies have suggested that rapid inward plasma flows may be controlling the production of their most energetic electrons. However, rapid plasma inflows languish in the planet’s inner magnetosphere, and they are not spatially appealing as a mechanism to form the belts. Here we show that slow, global-scale flows resulting from transient noon-to-midnight electric fields successfully explain the discretized flux spectra at quasi- and fully relativistic energies, and that they are ultimately responsible for the bulk of the highest energy electrons trapped at Saturn. This finding is surprising, given that plasma flows at Saturn are dominated by the planetary rotation; these weak electric field perturbations were previously considered impactful only over a very narrow electron energy range where the magnetic drifts of electrons cancel out with corotation. We also find quantitative evidence that ultrarelativistic electrons in Jupiter's radiation belts are accelerated by the same mechanism. Given that similar processes at Earth drive a less efficient electron transport compared to Saturn and Jupiter, the conclusion is emerging that global-scale electric fields can provide powerful relativistic electron acceleration, especially at strongly magnetized and fast-rotating astrophysical objects.

Subtraction Method for an Effective Quasi-monoenergetic Neutron Beam by Using Continuous Energy Spectra

The cross sections of 89Y(n, 3n)87m,87gY and 209Bi(n, 4n)206Bi reactions at a neutron energy of 30 MeV are measured by making use of neutron beams of continuous energy spectra and a subtraction method. By impinging proton beams of 30 and 35 MeV to a thick beryllium target, neutron beams of continuous and broad energy spectra are produced and are guided to Y and Bi sample targets. The difference between the two neutron spectra generated by two neighboring proton energies is found to be peaked in a narrow energy range and thus can be regarded as quasi-monoenergetic, which can be used to extract (n, xn) cross sections. The uncertainty in the neutron fluence is reduced by analyzing the activities of aluminum and niobium reference samples placed on top of the Y and Bi samples. The use of a subtraction method by employing neutron beams of continuous energy spectra gives us the 89Y(n, 3n)87m,87gY and 209Bi(n, 4n)206Bi cross sections in fair agreement with the existing experimental data and nuclear data libraries.

Redox Metal-Ligand Cooperativity Enables Robust and Efficient Water Oxidation Catalysis at Neutral pH with Macrocyclic Copper Complexes.

Water oxidation catalysis stands out as one of the most important reactions to design practical devices for artificial photosynthesis. Use of late first-row transition metal (TM) complexes provides an excellent platform for the development of inexpensive catalysts with exquisite control on their electronic and structural features via ligand design. However, the difficult access to their high oxidation states and the general labile character of their metal-ligand bonds pose important challenges. Herein, we explore a copper complex (12-) featuring an extended, π-delocalized, tetra-amidate macrocyclic ligand (TAML) as water oxidation catalyst and compare its activity to analogous systems with lower π-delocalization (22- and 32-). Their characterization evidences a special metal-ligand cooperativity in accommodating the required oxidative equivalents using 12- that is absent in 22- and 32-. This consists of charge delocalization promoted by easy access to different electronic states at a narrow energy range, corresponding to either metal-centered or ligand-centered oxidations, which we identify as an essential factor to stabilize the accumulated oxidative charges. This translates into a significant improvement in the catalytic performance of 12- compared to 22- and 32- and leads to one of the most active and robust molecular complexes for water oxidation at neutral pH with a kobs of 140 s-1 at an overpotential of only 200 mV. In contrast, 22- degrades under oxidative conditions, which we associate to the impossibility of efficiently stabilizing several oxidative equivalents via charge delocalization, resulting in a highly reactive oxidized ligand. Finally, the acyclic structure of 32- prevents its use at neutral pH due to acidic demetalation, highlighting the importance of the macrocyclic stabilization.

The effect of autoionization on the HBr+ X 2Π3/2,1/2 state photoelectron angular distributions

• Photoelectron angular distributions of the HBr + X state have been measured. • Photoelectron anisotropy parameters affected by autoionizing Rydberg states. • X state threshold electron spectrum exhibits partially resolved rotational structure. • Rydberg states observed in ion yield. A double-imaging photoelectron-photoion spectrometer and synchrotron radiation have been used to measure the HBr + X 2 Π 3/2 v + = 0, 1, 2 and the 2 Π 1/2 v + = 0 state photoelectron angular distributions, as characterized by the anisotropy parameter β , the total ion yield, and the threshold photoelectron spectrum. Particular attention has been focussed on the photon energy range between the 2 Π 3/2 and the 2 Π 1/2 spin–orbit components of the ground ionic state. This region encompasses Rydberg states, belonging to series converging onto the upper 2 Π 1/2 ionization limit, which may decay by autoionization into the 2 Π 3/2 ionization continuum. A detailed study has been performed on the effects of autoionization on the 2 Π 3/2 v + = 0 state photoelectron angular distributions. The observed energy dependent variations in the β -values exhibit a regular pattern that correlates with excitation into members of a very broad d-type Rydberg series. Additional rapid variations in the β -parameters, which occur over a narrow energy range, appear to coincide with sharp autoionizing Rydberg states belonging to s, p and d series. The present experimental results for the HBr + X 2 Π 3/2 v + = 0 state photoelectron anisotropy parameter are compared to previously reported theoretical predictions and to earlier studies of the Kr + 4p 5 2 P 3/2 state β -parameter. The threshold photoelectron spectrum of the X 2 Π 3/2 v + = 0 band exhibits partially resolved rotational structure. A simulation of this structure yields an ionization threshold of 11.6673 ± 0.0010 eV, which is consistent with previous measurements.

Hydroxychloroquine and curcumin conjugates as multifunctional co drugs for the potential treatment of COVID-19: An in-silico based study

The present study has been undertaken to search the novel co drugs for fighting against the COVID-19 disease through an in- silico approach. We have designed eight co drugs by merging two drugs namely hydroxychloroquine, used in the treatment of COVID-19 and curcumin an immuno modulator. The two drugs were linked through a bio-cleavable hydrolyzable linker by three-step process. The designed co drugs were subjected for molecular docking studies to know their therapeutic efficacy against the COVID-19 main protease (Mpro) and Interleukin-1β. The designed co drugs have a promising binding affinity towards Mpro in the narrow range of binding energies between -28.2498 to -35.8648 kcal/mol when compared to the standard Remdesivir which has -21.8600 kcal/mol. Similarly the binding energies of designed co drugs against Interleukin -1β range between -25.8032 to -34.6973 kcal/mol when compared to the standard curcumin which has -17.3274 kcal/mol. Our findings demonstrated that the designed co drugs may be useful for the treatment of viral respiratory infection due to their additive therapeutic actions on the viral protein and modulating the immune response synergistically.