Photoionization Cross Sections Research Articles

The combined effects of electric field and embedded dielectric matrix on the electronic and optical properties in Ge/SiGe core/shell quantum dots and its SiGe/Ge inverted structure

In this study, the binding energy (BE) and photoionization cross-section (PICS) coefficients in a Ge/Si0.15Ge 0.85 core/shell quantum dots (CSQDs) and in its inverted structure Si0.15Ge0.85 / Ge (ICSQDs) are studied. The influence of the hydrogenic impurity and capped matrix are taken into account. The electronic states and their related eigenfunctions are computed by solving the three-dimensional Schrödinger equation under the framework of the effective mass approximation (E.M.A) using the variational dimensional. The influence of the core radius and electric field strength on the BE and PICS are investigated. The numerical results reveal that the optoelectronic properties are considerably affected by the electric field strength (EF), immersed oxide matrix (OM) and geometric parameter. The obtained results prove that the PICS magnitude increases as the core radius increases and its resonant peak moves towards the lower energies for Ge/Si0.15Ge0.85 CSQDs structure, and increases as the core radius decreases and its resonant peak experiences a blue shift with increasing core radius for Si0.15Ge 0.85/ Ge ICSQDs. Moreover, with the effects of the surrounding oxide matrix and electric field strength, the PICS magnitude is improved and their resonant peak suffers a redshift.

Rotating effects on the photoionization cross-section of a 2D quantum ring

In this article, we investigate the nonrelativistic quantum motion of a charged particle within a rotating frame, taking into account the Aharonov–Bohm (AB) effect and a uniform magnetic field. Our analysis entails the derivation of the equation of motion and the corresponding radial equation to describe the system. Solving the resulting radial equation enables us to determine the eigenvalues and eigenfunctions, providing a clear expression for the energy levels. Furthermore, our numerical analysis highlights the substantial influence of rotation on both energy levels and optical properties. Specifically, we evaluate the photoionization cross-section with and without the effects of rotation. To elucidate the impact of rotation on the photoionization process of the system, we present graphics that offer an appealing visualization of the intrinsic nature of the physics involved.

Thermal decomposition study of 1,3-dioxolane as a representative of battery solvent

As industrial compounds and organic solvent, 1,3-dioxolane (C3H6O2) is used in lithium-ion batteries arousing extensive interest. The pyrolysis of C3H6O2 at 150 torr pressure was conducted in the temperature range of 743–1013 K. In order to quantify the major products, experimental measurements of the photoionization cross-section (PICS) and photoionization efficiency (PIE) for C3H6O2 were carried out by using synchrotron radiation photoionization mass spectrometry (SR-PIMS). Twenty-three intermediates were detected in pyrolysis of C3H6O2 including the newly observed ketene, acetaldehyde, ethenol, ethanol, dimethyl ether, diacetylene and 2-propen-1-ol which played important roles in developing mechanism. The H-abstraction of C3H6O2 by H, CH3 and OH radicals were studied via high level ab initio calculations. EStokTP code was used to find and calculate optimal geometries, vibration frequencies and intrinsic reaction coordinate (IRC) at the theory level of M06–2X/6–311+G(d,p). Conventional transition state theory (TST) was used and Rice-Ramsperger-Kassel-Marcus/Master Equation (RRKM/ME) was solved to obtain rate coefficients. For H-abstraction by H and CH3, the rates are increasing versus temperature, and rates of H-abstraction by OH show different tendency. These rate parameters were used to update the model of C3H6O2, which could well predict the ignition delay times (IDTs) in shock tube and oxidation data in jet stirred reactor (JSR) from literature. For the pyrolysis, H-abstraction reactions by H, CH3 and OH and unimolecular reactions contribute to solvent decay. Detailed pathways of C3H6O2 decomposition were also given and analyzed through this experiment and previous literature. The findings, including the experimental data and the calculations will assist to better understand pyrolysis characteristics of C3H6O2 as well.

Further investigation of spatially resolved single grain quartz OSL and TL signals

The use of luminescence signals from single mineral grains for optical dating has become a valuable and frequently utilised tool in Quaternary Geochronology. Single grain luminescence dating is particularly beneficial in complex depositional settings, however the ability to measure single grain signals also offers the opportunity to assess intrinsic luminescence properties of individual mineral grains. The use of spatially resolved luminescence technologies such as an electron multiplier charge coupled device is of benefit when making luminescence measurements at single grain scales because they allow stimulation with light emitting diodes, and this offers a number of key benefits related to stimulation power when it comes to the assessment of characteristics such as optically stimulated luminescence (OSL) decay rate and the calculation of parameters such as the fast ratio and photo ionisation cross-sections. In this paper, the intra- and inter-sample variability of sensitised single grain thermoluminescence (TL) and OSL signals is considered. A comparison between TL and OSL signals is undertaken, as well as calculation of the fast ratio, OSL component photo ionisation cross-sections, thermal stability, and characteristic dose for a suite of quartz samples from a range of geographic locations and depositional settings. For these heated signals, key findings include the lack of relationship between OSL signal intensity and dominance of the fast component, the fitting of two components (a fast and slow component) is the most common fit for single grain OSL signals, characteristic doses from fast dominated signals suggesting saturation at c. 150 Gy, and the identification of the ultrafast OSL component. Intra-sample variability across all measured parameters is observed, suggesting that for this suite of samples, variability is the norm rather than the exception, and that the intrinsic luminescence characteristics of quartz are variable and diverse.

Quantifying the U 5f covalence and degree of localization in U intermetallics

A procedure for quantifying the U 5f electronic covalency and degree of localization in U intermetallic compounds is presented. To this end, bulk sensitive hard and soft x-ray photoelectron spectroscopy were utilized in combination with density-functional theory (DFT) plus dynamical mean-field theory (DMFT) calculations. The energy dependence of the photoionization cross sections allows the disentanglement of the U 5f contribution to the valence band from the various other atomic subshells so the computational parameters in the DFT+DMFT can be reliably determined. Applying this method to UGa2 and UB2 as model compounds from opposite ends of the (de)localization range, we have achieved excellent simulations of the valence band and core-level spectra. The width in the distribution of atomic U 5f configurations contributing to the ground state, as obtained from the calculations, quantifies the correlated nature and degree of localization of the U 5f. The findings permit answering the longstanding question why different spectroscopic techniques give seemingly different numbers for the U 5f valence in intermetallic U compounds. Published by the American Physical Society 2024

Continuum spectrum of atomic lithium in a magnetic field of white dwarfs

ABSTRACT This paper reports on computational results of continuum spectra of atomic lithium in white-dwarf-strength magnetic fields. The adiabatic-basis-expansion method with R-matrix propagation has been used to study photoionization of magnetized alkali metal atoms. The R-matrix propagation technique and the two-dimensional matching scheme were utilized to obtain wavefunctions of the continuum states. Cross-sections of photoionization are calculated for lithium atoms in magnetic fields. Continuum spectra for its various bound-free transitions in magnetic white dwarf stars are presented as a function of field strengths ranging from 11.75 to 117.50 MG. Comparison is made between continuum spectra of diamagnetic hydrogen and lithium atoms. The comparison shows good agreement or remarkable difference for final continuum states with different symmetries in the photoionization processes concerned. A detailed analysis has been performed to understand the obtained results. The good agreement displayed manifests the reliability of the extended adiabatic-basis-expansion method. This method is suited to produce a large number of photoionization cross-section data for alkali metal atoms in a strong magnetic field, and therefore can serve as a tool to simulate continuum spectra observed in the atmospheres of magnetic white dwarfs with alkali metal atoms.

Two-photon laser-induced fluorescence study of the CO B 1Σ+ (v' = 0) state in a 4850K plasma plume: Modified molecular constants, evidence of predissociation, and J'-dependent photoionization.

We report the two-photon absorption laser-induced fluorescence rotational spectrum of the CO B 1Σ+ ← X 1Σ+ Hopfield-Birge system (v' = 0, v″ = 0) Q-branch in an ∼4850K, atmospheric pressure plasma torch plume at thermal equilibrium in both the quenching-dominated (low laser intensity) and photoionization-dominated (high laser intensity) regimes. We provide a detailed analysis of the photophysics in these two regimes using a rate equation approach and propose modeling considerations for them as well. In the experimental spectra, distinct rotational transitions up to J″ = 83 are observed, allowing analysis over a very large range of rotational states. Evidence of predissociation is observed for J' ≥ 64 and is likely due to the interaction with the D'1Σ+ electronic state, which has been proposed in the literature but never observed in the v' = 0 state. The line positions of higher rotational states show disagreement with line positions calculated from molecular constants in the available literature, suggesting the need for modifications to the constants, which are reported here. A shift in the B 1Σ+ ← X 1Σ+ absorption spectrum toward higher two-photon energy as a result of the second-order Stark shift was observed in the photoionization-dominated spectrum, and the second-order Stark shift cross section was estimated to be 7 ± 3 × 10-18 cm2. The mean photoionization cross section of the excited upper state was inferred by comparing the line broadening of the two spectra and was estimated to be 11 ± 7 × 10-18 cm2. In addition, weak J'-dependent variations of the photoionization cross section were observed and are reported here.

Energy levels and characteristic features in photoionization of Cl III using the R-matrix method

We report study of Cl III for its large number of fine structure bound levels, 890, with n ≤ 10 and l ≤ 9, and 1/2 ≤ j ≤ 19/2 of even and odd parities with spectroscopic designation and photoionization cross sections (σPI) of the levels revealing various characteristic features. Various resonant structures and the shapes of the background, and their interference in σPI are illustrated for the ground, excited equivalent electron, low and high lying excited levels with single valence electron, and effects of fine structure couplings. σPI of the ground level shows Rydberg series of resonances on smooth background, and of equivalent electron levels producing strong closely spaced Rydberg series of resonances belonging to the low lying core ion excitation thresholds. They will impact applications in low temperature plasma. For the single valence electron excited levels, we find that σPI of low lying excited states are dominated by Rydberg series of resonances and of high lying excited states exhibit prominent broad feature of Seaton resonances. Partial photoionization cross sections of the ground level for leaving the core ion in the ground and various excited levels are also presented for applications in plasma modeling. The study was carried out in relativistic Breit–Pauli R-matrix method using a large close coupling wave function expansion of 45 levels of the core ion configurations 3 s23 p2, 3 s3 p3, 3 s23 p3 d, 3 s23 p4 s, 3 s3 p23 d, and 3 p4 with closed 1s, 2s, 2p orbitals. They belong to the optimized set of 13 configurations of Cl IV, 3 s23 p2, 3 s3 p3, 3 s23 p3 d, 3 s23 p4 s, 3 s23 p4 p, 3 s23 p4 d, 3 s3 p23 d, 3 s3 p24 s, 3 s3 p24 p, 3 p4, 3 p33 d, 3 p34 s, and 3 p34 p. Cl III energies are in good agreement with measured values. σPI features of low lying levels were benchmark with observation carried out at Advanced Light Source at LBNL with very good agreement. The present set of high accuracy data should complete for any practical applications.

Photoionization process of the hydrogenlike carbon ion embedded in warm and hot dense plasmas.

Complicated many-body interactions between ions and surrounding particles exist in warm and hot dense plasmas. It will significantly alter the atomic structures and dynamic properties of the embedded ions. Recently, the atomic-state-dependent (ASD) screening model has been proposed and shown to be valid for investigating the screening effect in warm and hot dense plasmas over a wide range of electron densities and temperatures. By employing the ASD model, we investigate the photoionization process for the hydrogenlike carbon ion embedded in warm and hot dense plasmas with corresponding Coulomb coupling parameter ranges of 0.05 ≤ Γ ≤ 1.16, where Γ characterizes the ratio of the average potential to thermal energy. It is found that there are stronger plasma screening effects on the ionization energy and photoionization cross section due to the negative-energy electron distributions considered in the ASD model compared to those considering only free electrons. The present results from the ASD model show reasonable agreement with the classical Debye-Hückel (DH) model in weakly coupled plasmas. However, significant deviations of the ionization energy and cross section between these two models are observed in moderately and strongly coupled plasmas, due to the approximate treatment of the plasma-electron density distribution of the DH model. In the region of low photoelectron energies, the positions of the shape resonance peaks of the cross sections obtained from the ASD model differ significantly from those of the DH model due to the different screening effects.

IRSL properties of HfO2 obtained by the precipitation method and its correlation to ESR centres

Infrared-stimulated luminescence (IRSL) emission and its characterisation are reported for the first time for HfO2 synthesised by the precipitation method and its electron spin resonance (ESR) centres properties are shown in this study. IRSL spectrum has a broad emission band in the blue region, which is centred at about 2.49 eV. A similar emission was observed for the radiofluorescence (RF) with a band centred at 2.52 eV. RF signal intensity decreases with the readout temperature, which might indicate a thermal quenching process.IRSL signal is strongly affected by the readout temperature, as part of its emission is related to the presence of shallow traps (<100 °C). The IRSL shine-down curve is composed of two components with decay times of 15.7 and 800 s, and photoionisation cross-section values of about 1.20 × 10−19 and 2.35 × 10−21 cm2, respectively, based on IRSL carried out at 100 °C after 2 Gy of beta irradiation dose, using a general-order kinetic model. Dosimetric analyses indicated that there is a reproducible signal in IRSL, with a coefficient of variation lower than 9 % for repeatability and 3 % for reproducibility measurements. The dose-response curve has a linear trend in the dose range of 0.3–2.0 Gy. Regarding the photon energy study, it shows an overresponse for photo energy values below 200 keV. Fading of about 40 % after one day of storage was observed.Bleaching measurements indicated that the TL peaks located between 100 and 250 °C share the same trap levels as the IRSL ones. In addition, a possible charge transference is observed from the peak at 330 °C to lower temperature peaks. ESR analyses identified that oxygen vacancies of V+ type in a four-coordinated arrangement are induced by irradiation and are temperature-sensitive. Based on the bleaching and ESR measurements, it is reasonable to infer that V+ type vacancies are likely responsible for the IRSL, and its blue emission.

R-matrix calculations for opacities: IV. Convergence, completeness, and comparison of relativistic R-matrix and distorted wave calculations for Fe xvii and Fe xviii

To investigate the completeness of coupled channel (CC) Breit–Pauli R-matrix (BPRM) calculations for opacities we employ the relativistic distorted wave (RDW) method to complement (‘top-up’) and compare the BPRM photoionization cross sections for high- nℓ levels of both Fe xvii and Fe xviii . Good agreement is found with background photoionization cross sections using these two methods, which also ensures the correct matching of bound level cross sections for completeness. In order to top-up the CC-BPRM calculations, bound–bound transitions involving additional bound levels, and a large number of doubly-excited quasi-bound levels corresponding to BPRM autoionizing resonances described in the paper RMOPII are calculated using the RDW method. Photoionization cross sections in the high energy region are also computed and compared up to about 500 Ry, and contributions from higher core level excitations than BPRM are considered. The effect of configuration interaction is investigated, which plays a significant role in correctly reproducing some background cross sections. Due to the fact that the additional RDW levels correspond to high- nℓ bound levels that are negligibly populated according to the Mihalas–Hummer–Däppen equation-of-state (paper I), the effect on opacities is expected to be small.

R-matrix calculations for opacities: III. Plasma broadening of autoionizing resonances

A general formulation is employed to study and quantitatively ascertain the effect of plasma broadening of intrinsic autoionizing (AI) resonances in photoionization cross sections. In particular, R-matrix data for iron ions described in the previous paper in the RMOP series (RMOP-II, hereafter RMOP2) are used to demonstrate underlying physical mechanisms due to electron collisions, ion microfields (Stark), thermal Doppler effects, core excitations, and free–free transitions. Breit–Pauli R-matrix cross sections for a large number of bound levels of Fe ions are considered, 454 levels of Fe XVII, 1184 levels of Fe XVIII and 508 levels of Fe XIX. Following a description of theoretical and computational methods, a sample of results is presented to show significant broadening and shifting of AI resonances due to extrinsic plasma broadening as a function of temperature and density. The redistribution of AI resonance strengths broadly preserves their integrated strengths as well as the naturally intrinsic asymmetric shapes of resonance complexes which are broadened, smeared and flattened, eventually dissolving into the bound-free continua.

R-matrix calculations for opacities: I. Methodology and computations

An extended version of the R-matrix methodology is presented for calculation of radiative parameters for improved plasma opacities. Contrast and comparisons with existing methods primarily relying on the distorted wave approximation are discussed to verify accuracy and resolve outstanding issues, particularly with reference to the opacity project (OP). Among the improvements incorporated are: (i) large-scale Breit–Pauli R-matrix calculations for complex atomic systems including fine structure, (ii) convergent close coupling wave function expansions for the (e + ion) system to compute oscillator strengths and photoionization cross sections, (iii) open and closed shell iron ions of interest in astrophysics and experiments, (iv) a treatment for plasma broadening of autoionizing resonances as function of energy-temperature-density dependent cross sections, (v) a ‘top-up’ procedure to compare convergence with R-matrix calculations for highly excited levels, and (vi) spectroscopic identification of resonances and bound (e + ion) levels. The present R-matrix monochromatic opacity spectra are fundamentally different from OP and lead to enhanced Rosseland and Planck mean opacities. An outline of the work reported in other papers in this series and those in progress is presented. Based on the present re-examination of the OP work, opacities of heavy elements might require revisions in high temperature-density plasma sources.

R-Matrix calculations for opacities: II. Photoionization and oscillator strengths of iron ions Fe xvii, Fe xviii and Fe xix

Iron is the dominant heavy element that plays an important role in radiation transport in stellar interiors. Owing to its abundance and large number of bound levels and transitions, iron ions determine the opacity more than any other astrophysically abundant element. A few iron ions constitute the abundance and opacity of iron at the base of the convection zone (BCZ) at the boundary between the solar convection and radiative zones and are the focus of the present study. Together, Fe xvii, Fe xviii and Fe xix represent 85% of iron ion fractions, 20%, 39% and 26% respectively, at the BCZ physical conditions of temperature T ∼ 2.11×106 K and electron density Ne = 3.1×1022 c.c. We report the most extensive R-matrix atomic calculations for these ions for bound–bound and bound–free transitions, the two main processes of radiation absorption. We consider wavefunction expansions with 218 target or core ion fine structure levels of Fe xviii for Fe xvii, 276 levels of Fe xix for Fe xviii, in the Breit–Pauli R-matrix (BPRM) approximation, and 180 LS terms (equivalent to 415 fine structure levels) of Fe xx for Fe xix calculations. These large target expansions, which include core ion excitations to n = 2,3,4 complexes, enable accuracy and convergence of photoionization cross sections, as well as the inclusion of high lying resonances. The resulting R-matrix datasets include 454 bound levels for Fe xvii, 1,174 levels for Fe xviii, and 1,626 for Fe xix up to n⩽ 10 and l = 0–9. Corresponding datasets of oscillator strengths for photoabsorption are: 20 951 transitions for Fe xvii, 141 869 for Fe xviii, and 289 291 for Fe xix. Photoionization cross sections have been obtained for all bound fine structure levels of Fe xvii and Fe xviii, and for 900 bound LS states of Fe xix. Selected results demonstrating prominent characteristic features of photoionization are presented, particularly the strong Seaton photoexcitation-of-core resonances formed via high-lying core excitations with Δn=1 that significantly impact bound–free opacity.

Oscillator strengths, intracenter absorption and photoionization cross sections of optical transitions of shallow donors in silicon

Oscillator strengths, intracenter absorption and photoionization cross sections of optical transitions of shallow donors in silicon

Photoelectron angular distribution of benzene: Can the asymmetry parameter be considered a benchmark?

The calculated asymmetry parameter (β) and photoionisation cross sections for eight outermost orbitals (1e1g, 3e2g, 1a2u, 3e1u, 1b2u, 2b1u, 3a1g, and 2e2g) of benzene, in the gas phase, are presented in the range from threshold to 35 eV. The Schwinger Variational Method with Padé approximants was employed to generate the continuum wavefunction of photoelectrons and the dipole matrix transition was computed in the velocity (V) and length (L) approach of the dipole operator. This operator in V or L form does not affect significantly β values in the energy range studied. The cross sections in V form produce lower magnitudes than L and are closer to the measurements. The resonance peaks were observed in the cross sections for some orbitals and their positions were not affected by the dipole approach. Finally, symmetry analysis is done on the partial cross sections to assign the main contributing final state to the resonance feature and also link this to the minimum in the asymmetry parameter. The comparison of our results with other theories has, in general, good qualitative and some quantitative agreement. For some orbitals (1a2u, 2b1u), severe disagreements between theory and experiment are highlighted. Some possible causes for these differences are pointed out. Because of this, we conclude that some asymmetry parameters and PICS for benzene, in ionisation studies, cannot yet be considered as a benchmark and will be necessary further investigation to clarify such discrepancies.

Photoionization cross sections measurements of the excited states of lutetium and ytterbium in the near threshold region.

In this work, the threshold photoionization cross sections from the excited states of lutetium and ytterbium atoms were investigated by the laser pump-probe scheme under the condition of saturated resonant excitation. We obtained the resonance enhanced multiphoton ionization spectra of the lutetium and ytterbium atoms of the lanthanide metals in the range of 307.50-312.50nm and 265.00-269.00nm, respectively; the photoionization cross sections of the 5d6s(1D)6p(2D05/2) and 5d6s(3D)6p(2P01/2) states of lutetium and the 4f13(2F0)5d6s2(J = 1) states of ytterbium above threshold regions (0.4-1.6eV) were measured, and measured values ranged from 2.3 ± 0.2 to 17.7 ± 1.5 Mb.

Enhancement of the NORAD-Atomic-Data Database in Plasma

We report recent enhancements to the online atomic database at the Ohio State University, NORAD-Atomic-Data, that provide various parameters for radiative and collisional atomic processes dominant in astrophysical plasma. NORAD stands for Nahar Osu RADiative. The database belongs to the data sources, especially for the latest works, of the international collaborations of the Opacity Project and the Iron Project. The contents of the database are calculated values for energies, oscillator strengths, radiative decay rates, lifetimes, cross-sections for photoionization, electron-ion recombination cross-sections, and recombination rate coefficients. We have recently expanded NORAD-Atomic-Data with several enhancements over those reported earlier. They are as follows: (i) We continue to add energy levels, transition parameters, cross-sections, and recombination rates for atoms and ions with their publications. (ii) Recently added radiative atomic data contain a significant amount of transition data for photo-absorption spectral features corresponding to the X-ray resonance fluorescence effect, showing prominent wavelength regions of bio-signature elements, such as phosphorus ions, and emission bumps of heavy elements, such as of lanthanides, which may be created in a kilonova event. We are including (iii) collisional data for electron-impact-excitation, (iv) experimental data for energies and oscillator strengths for line formation, (v) experimental cross-sections for photoionization that can be applied for benchmarking and other applications, and (vi) the introduction of a web-based interactive feature to calculate spectral line ratios at various plasma temperature and density diagnostics, starting with our recently published data for P II. We presented a summary description of theoretical backgrounds for the computed data in the earlier paper. With the introduction of experimental results in the new version of NORAD, we present a summary description of measurement of high-resolution photoionization cross-sections at an Advanced Light Source of LBNL synchrotron set-up and briefly discuss other set-ups. These additions should make NORAD-Atomic-Data more versatile for various applications. For brevity, we provide information on the extensions and avoid repetition of data description of the original paper.

A Missing Piece of the E‐Region Puzzle: High‐Resolution Photoionization Cross Sections and Solar Irradiances in Models

AbstractMost ionospheric models cannot sufficiently reproduce the observed electron density profiles in the E‐region ionosphere, since they usually underestimate electron densities and do not match the profile shape. Mitigation of these issues is often addressed by increasing the solar soft X‐ray flux which is ineffective for resolving data‐model discrepancies. We show that low‐resolution cross sections and solar spectral irradiances fail to preserve structure within the data, which considerably impacts radiative processes in the E‐region, and are largely responsible for the discrepancies between observations and simulations. To resolve data‐model inconsistencies, we utilize new high‐resolution (0.001 nm) atomic oxygen (O) and molecular nitrogen (N2) cross sections and solar spectral irradiances, which contain autoionization and narrow rotational lines that allow solar photons to reach lower altitudes and increase the photoelectron flux. This work improves upon Meier et al. (2007, https://doi.org/10.1029/2006gl028484) by additionally incorporating high‐resolution N2 photoionization and photoabsorption cross sections in model calculations. Model results with the new inputs show increased O+ production rates of over 500%, larger than those of Meier et al. (2007, https://doi.org/10.1029/2006gl028484) and total ion production rates of over 125%, while production rates decrease by ∼15% in the E‐region in comparison to the results obtained using the cross section compilation from Conway (1988, https://apps.dtic.mil/sti/pdfs/ADA193866.pdf). Low‐resolution molecular oxygen (O2) cross sections from the Conway compilation are utilized for all input cases and indicate that is a dominant contributor to the total ion production rate in the E‐region. Specifically, the photoionization contributed from longer wavelengths is a main contributor at ∼120 km.

Examining the influence of magnetic field on a donor dopant’s photoionization cross-section in a double quantum box

This study systematically explored the binding energy and the photoionization cross-section (PCS) of a hydrogenic shallow donor impurity within a GaAs double quantum box structure incorporated into a Ga(1−x)Alx As matrix under the influence of an external intense magnetic field. The computations are performed using the effective-mass approximation (EMA) and the finite element method (FEM), taking into account a finite potential across all surfaces of the nanosystem. The results emphasize the significant role of the magnetic field, primarily in enhancing the donor binding energy within the double quantum box system. We demonstrate that increasing the magnetic field results in an augmentation of binding energy across various aluminum concentrations. The PCS of a shallow donor impurity undergoes a blue shift when shifted from the barrier center to the box center, attributed to the increased binding energy. When the double quantum box is subjected to a magnetic field effect, the amplitude peaks of PCS show an elevation coupled with a blue shift. By setting magnetic field values at 0 T, 35 T, or 70 T and varying aluminum concentrations, we observe a shift in the PCS towards higher energy levels along with an increase in peak amplitude. We also study the PCS of the donor impurity as a function of photon energy, mainly examining the effects of box width and barrier width modifications in the double quantum box.