Increase In Electron Temperature Research Articles

Hybrid simulation study on ion heating by low-frequency wave excited in a field-reversed configuration

Abstract In this paper, we use hybrid simulation to elucidate the plasma heating mechanism due to waves excited in Field-Reversed Configuration plasma(FRC). The plasma parameters are a separatrix radius of 0.16 m and a separatrix length of 1.16 m (x-point position is z = ±0.57 m). The wave excitation antenna consists of two loop antennas with a radius of 0.3 m and is placed at a position of z = ±0.5 m. The current waveform of the antenna is a sine wave with a maximum current value of 30 kA and a frequency of 160 kHz. The simulation results showed that the excited waves caused compression/expansion of the plasma, and at the same time, the temperature of the plasma increased or decreased at the compressed/expanded position. When waves are applied, a 23% increase in the volume-averaged ion temperature in the separatrix is observed compared to the case without waves applied. On the other hand, no increase in electron temperature is observed. For the electron fluid, the adiabatic condition is well established, and temperature changes are observed as the plasma compressed and expanded. On the other hand, for ions, kinetic energy perpendicular to the magnetic field lines increases during compression, and part of this energy is transferred to the energy of the parallel component by collisionless pitch angle scattering, resulting in heating due to the so-called magnetic pumping.

Effects of turbulence spreading and symmetry breaking on edge shear flow during sawtooth cycles in J-TEXT tokamak

The effect of sawteeth on plasma performance and transport in the plasmas of tokamak is an important issue in the fusion field. Sawtooth oscillations can trigger heat and turbulence pulses that propagate into the edge plasmas, and thus enhance the edge shear flow and induce a transition from low confinement mode to high confinement mode. The influences of turbulence spreading and symmetry breaking on edge shear flow with sawtooth crashes are observed in the J-TEXT tokamak. The edge plasma turbulence and shear flow were measured using a fast reciprocating electrostatic probe array. The experimental data were analyzed using methods such as conditional average and probability distribution function. After sawtooth crashes, the heat and turbulence pulses in the core propagate to the edge, with the turbulence pulse being faster than the heat pulse. Figures 1 (a)-(e) show the core electron temperature, and the edge electron temperature, turbulence intensity, turbulence drive and spreading rates, Reynolds stress and its gradient, and shearing rates, respectively. Following sawtooth crashes, the edge electron temperature increases and the edge turbulence is enhanced, with turbulence preceding temperature. The enhanced edge turbulence is mainly composed of two parts: turbulence driven by local gradient and turbulence spreading from core to edge. The development of the estimated turbulence spreading rates is prior to that of the turbulence driving rates. The increase in the turbulence intensity can cause the enhancements of the turbulent Reynold stresses and its gradient, thereby enhancing shear flows and radial electric fields. Turbulence spreading leads to the development of edge Reynolds stresses and shear flow faster than edge electron temperature. The Reynolds stress arises from the symmetry breaking of the turbulence wave number spectrum. After sawtooth collapse, the joint probability density function of radial and poloidal wave numbers of turbulence intensity became highly skewed and anisotropic, exhibiting strong asymmetry, as seen in the figures 1 (f) and (g). The development of turbulence spreading flux at the edge is also prior to the particle flux driven by turbulence, indicating that turbulent energy transport is not simply accompanied by turbulent particle transport. These results show that turbulence spreading and symmetry breaking can enhance turbulent Reynolds stress, thereby driving shear flows, after sawtooth crashes.

Nonthermal solid-solid phase transition in ferromagnetic iron

We posit the existence of a nonthermal phase transition in iron, driven by a loss of ferromagnetic ordering on ultrafast timescales with increasing electron temperature. The transition corresponds to a solid-solid bcc to fcc phase transformation and takes place at an electron temperature of 0.62 eV while the ion lattice remains near room temperature. The bcc structure initially undergoes phonon softening during the magnetic transformation, followed by a solid-solid phase transition to the fcc structure, and a subsequent hardening of phonon modes. We present a detailed physical picture of the process, supported by finite-temperature density functional theory simulations of the phonon dispersion curves, electronic density of states, and thermodynamic free energy. Published by the American Physical Society 2024

Effect of external magnetic field inhomogeneity on the nonlinear absorption of intense laser pulse in inhomogeneous warm plasma

This paper studies the propagation of an intense laser pulse and the collisional absorption in an inhomogeneous warm plasma by taking into account the external magnetic field inhomogeneity and the ponderomotive force. The calculations are carried out and compared for different magnetic field strengths and their various configurations. For this purpose, using the hydrodynamic equations, the electron density and hence the effective dielectric permittivity of the magneto-active warm plasma are derived and the nonlinear wave equation is solved through the numerical method of Runge–Kutta. The results show that increasing the strength of the external magnetic field causes an increase in the absorption coefficient and the linear magnetic field has a higher influence on the absorption coefficient with respect to the wiggler and constant magnetic fields. Moreover, when the electron temperature increases, the amplitude of the laser field and the absorption coefficient are increased and the spatial damping rate of the laser pulse takes a peak in the plasma. The results also indicate that increasing the energy of the laser pulse causes a decrease in the nonlinear absorption, and the laser energy spatial damping is significantly decreased in contrast to the growth of the amplitude of the laser field. A qualitative comparison of the results indicates that if a linear magnetic field is applied in the same direction of the laser propagation, the collisional absorption rate will be larger with respect to the other magnetic fields. Moreover, the difference in the influence of the mentioned magnetic fields on the collisional absorption increases with increasing the electron temperature and normalized cyclotron frequency and decreases with increasing laser intensity.

Electron temperature and ion density distribution on a vertical section in a weakly magnetized inductively coupled plasma

In this study, the distributions of electron temperature and ion density on a vertical section in a weakly magnetized inductively coupled plasma were measured using radially movable floating probes placed at different axial positions. The chamber used in this experiment included two cylindrical parts: a smaller radius top part with a planar antenna on the top quartz window and a larger radius downstream part. A magnet coil around the chamber top part maintained a divergent magnetic field in the discharge region. As the current in the magnet coil increased, the magnetic field also increased. Due to the variations of the radio frequency electric field in the plasma, the increase in electron temperature can be divided into different stages. At the higher magnetic field, the electric field of the electrostatic wave can increase electron temperature at the chamber center axial. Also, since the electron cyclotron resonance (ECR) heating in the chamber downstream part changed with the magnetic field, the maximum ion density was observed when the magnetic field around the bias electrode was slightly larger than the ECR magnetic condition. The reasons for these variations were verified in the plasma numerical simulations. The ion flux distribution measured on the bias electrode can change from a center-high distribution to an M-shape distribution with the increased magnetic field.

CONCERNING EFFECTS OF INERT CARRIER GAS ON DENSITIES OF ACTIVE SPECIES AND ZrO2 ETCHING KINETICS IN CHLORINE PLASMA

In this work, we investigated the influence of inert carrier gas on electro-physical plasma parameters, steady-state densities of active species and kinetics of their interaction with ZrO2 under the condition of “soft” reactive-ion etching in chlorine. This regime assumes the lower-than-usual negative bias voltage in order to reduce both ion bombardment energy and etched surface damage. The combination of plasma diagnostics by Langmuir probes and 0-dimensional plasma modeling allowed one to analyze formation and decay kinetics for neutral and charged species at various gas mixing ratios. It was found that the mixing of Cl2 with Ar or He at constant total gas pressure a) causes an increase in both electron temperature and plasma density; b) increases the Cl2 dissociation degree through the acceleration of electron-impact processes; and c) intensifies the ion bombardment by the change of ion flux. From etching experiments, it was found also that the ZrO2 etching rate is mostly composed by its chemical component, but does not correlate with the change in the Cl atom flux. The latter reveals that a) the dominant ZrO2 etching mechanism is the ion-assisted chemical reaction and b) an increase in the effective reaction probability toward Ar or He rich plasmas reflects the acceleration of ion-induced heterogeneous effects, such as the destruction of Zr-O bonds and/or the desorption of low-volatile ZrClx compounds. The lower neutral/charged ratio obtained in Ar-containing plasma allows one to assume the more anisotropic etching. It was shown that above findings are surely valid in the pressure range of 4–12 mTorr as well at bias powers of 100 – 300 W. For citation: Efremov A.M., Smirnov S.A., Betelin V.B., Kwon K.-H. Concerning effects of inert carrier gas on densities of active species and ZrO2 etching kinetics in chlorine plasma. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 40-54. DOI: 10.6060/ivkkt.20246711.7073.

Influence of Applied Discharge Voltage and Gas Flow Rate on Nickel Plasma Jet Parameters Diagnosed by Optical Emission Spectroscopic Technique

Abstract: In this work, we measure the plasma parameters by using an AC high-voltage power supply that generates a non-thermal plasma jet system at atmospheric pressure. A nickel (Ni) metal strip, with dimensions of 1.5 × 10 cm2, was connected to the anode electrode of the AC power supply. This nickel strip was immersed in a flask with a small amount of distilled water positioned below the plasma plume nozzle. Optical emission spectroscopy (OES) was used to diagnose the plasma system at different argon gas flow rates (1-5 L/min) and varying applied voltage values (11-15 kV). It is significant to know the processes accompanying plasma generation to measure their parameters which include the electron temperature (Te), electron number density (ne) of the plasma, Debye length (λD), and plasma frequency (fp). Our results showed an increase in the intensity of spectral lines with the increase in applied discharge voltage (11-15 kV). The maximum peak for ArI was observed at a wavelength of 811.531 nm, and the maximum peaks for nickel (Ni) were observed at wavelengths of 285.21 and 519.70 nm. Also, the results indicated a gradual increase in electron temperature (Te) and electron density (ne) values at the applied voltage of 0.403-0.468 eV. Likewise, the electron density (ne) was in the range of (11.486-13.851) × 1017 cm-3. Keywords: Atmospheric plasma jet, Nickel (Ni) plasma parameters, Electron temperature, Spectroscopic optical emission (OES).

Expulsion of runaway electrons using ECRH in the TCV tokamak

Abstract Runaway electrons (REs) are a concern for tokamak fusion reactors from discharge startup to termination. A sudden localized loss of a multi-megaampere RE beam can inflict severe damage to the first wall. Should a disruption occur, the existence of a RE seed may play a significant role in the formation of a RE beam and the magnitude of its current. The application of central electron cyclotron resonance heating (ECRH) in the Tokamak à Configuration Variable (TCV) reduces an existing RE seed population by up to three orders of magnitude within only a few hundred milliseconds. Applying ECRH before a disruption can also prevent the formation of a post-disruption RE beam in TCV where it would otherwise be expected. The RE expulsion rate and consequent RE current reduction are found to increase with applied ECRH power. Whereas central ECRH is effective in expelling REs, off-axis ECRH has a comparatively limited effect. A simple 0-D model for the evolution of the RE population is presented that explains the effective ECRH-induced RE expulsion results from the combined effects of increased electron temperature and enhanced RE transport.

Simulation of Low-Pressure Inductively Coupled Plasma with Displacement Potential and Gas Flow

The dependence of the parameters of low-pressure inductively coupled argon plasma (13.3–113 Pa) and field frequency of 13.5٦ MHz at the coil on the potential applied to the electrode and on gas flow rate up to 4000 sccm is numerically studied. The model is developed in the COMSOL Multiphysics environment and verified with experimental data, as well as over the Knudsen number. As a result of a numerical experiment, it is revealed as follows: when the displacement potential increases linearly, the density of charged particles increases exponentially and a slight increase in the electron temperature is observed; when the gas flow rate increases linearly, the density of charged particles increases exponentially, the density of excited states has an extremum at 2000 sccm, and the gas and electron temperature increases linearly.

Hot Electrons in a Steady State: Interband vs Intraband Excitation of Plasmonic Gold.

Understanding the dynamics of "hot", highly energetic electrons resulting from nonradiative plasmon decay is crucial for optimizing applications in photocatalysis and energy conversion. This study presents an analysis of electron kinetics within plasmonic metals, focusing on the steady-state behavior during continuous-wave (CW) illumination. Using an inelastic spectroscopy technique, we quantify the temperature and lifetimes of distinct carrier populations during excitation. A significant finding is the monotonic increase in hot electron lifetime with decreases in electronic temperature. We also observe a 1.22× increase in hot electron temperature during intraband excitation compared to interband excitation and a corresponding 2.34× increase in carrier lifetime. The shorter lifetimes during interband excitation are hypothesized to result from direct recombination of nonthermal holes and hot electrons, highlighting steady-state kinetics. Our results help bridge the knowledge gap between ultrafast and steady-state spectroscopies, offering critical insights for optimizing plasmonic applications.

Variations of plasma potential in RF discharges with DC-grounded electrode

The self-bias voltage Vbias and the plasma potential Vp are the key parameters to control plasma-wall interactions in radio-frequency (RF) asymmetric plasma discharges. Knowing these two parameters allows to monitor the ion energy distribution on the electrode surface. However, in a direct current (DC) coupled plasma, the plasma potential increased to hundreds of volts while no more Vbias developed on the driven electrode. In addition, the plasma potential is strongly impacted by the electrode-wall area ratio. Several analytical or semi-analytical models exist to explain this phenomenon and to approximate the plasma potential, knowing the electrode-wall area ratio considering capacitive sheaths or a combination of resistive and capacitive sheaths. The Vp and several other plasma parameters were investigated experimentally with a Langmuir probe and a Retarding field energy analyser for different electrode/wall area ratios in low-temperature RF plasma. The validity of the models was studied for an extensive range of area ratios with different pressures and RF driving amplitude. Moreover, the presence of strong stochastic heating of the plasma for area ratios below 6 was evidenced by an increased ion flux and an increased electron temperature.

Enhanced laser absorption and ion acceleration by boron nitride nanotube targets and high-energy PW laser pulses

Enhancing laser energy absorption with energy transfer to fast electrons is crucial for efficient laser-driven ion acceleration. In this work, we present an experimental demonstration of volumetric laser absorption using boron nitride nanotube (BNNT) targets with an average density of 15 of the solid density. We use a PW laser system operating at a pulse duration of 1.2 ps and an energy of 1.3 kJ, reaching intensities of 2 × 1019 Wcm−2 on target with moderate nanosecond contrast (109), to generate energetic ion streams from a 250 µm thick BNNT target. To characterize laser-accelerated ions, Thomson parabola spectrometers, CR-39 nuclear track detectors, and an electron spectrometer are employed. The results are compared to those achieved using flat targets made of polystyrene (PS) of the same thickness. The comparison reveals a 1.5-fold increase in proton maximum energy and a 2.5-fold increase in the maximum energy of heavy ions (C and N) when comparing the BNNT to PS. Moreover, the high-energy ion flux recorded at CR-39 is orders of magnitude higher for the BNNT after cutting off low-energy ions with Al filters. The enhanced ion acceleration is the result of a 2.3-fold increase in the electron temperature for BNNT, as measured by the electron spectrometer. These experimental findings are further validated through two-dimensional particle-in-cell simulations, which confirm the increase in electron temperature due to enhanced laser absorption ascribable to the low density and nanostructure of the BNNT target compared to the flat foil. Published by the American Physical Society 2024

Revisit of electron temperature effect on stimulated Brillouin scattering in homogenous plasma

Stimulated Brillouin scattering (SBS) has complex dependence on the plasma electron temperature via the Landau damping, particle trapping, and consequent nonlinear frequency shift. It is found from our numerical simulation that the SBS reflectivity in its saturation stage tends to increase with the plasma electron temperature within a certain range, although the linear growth rate of SBS normally reduces with the increasing electron temperature. This is because the phase velocity of an ion acoustic wave (IAW) increases with the electron temperature, which tends to reduce the Landau damping of the IAWs and hence reduce ion trapping. In the nonlinear saturation stage, ion trapping will modify the ion distribution function and induce a negative frequency shift in the IAW. This nonlinear frequency shift will break the three-wave coupling, thereby causing saturation of the SBS. With further increase in the electron temperature, however, electron trapping will dominate over ion trapping, which induces a positive frequency shift in the IAW and can lead to the SBS saturation as well. As a result, the SBS reflectivity first increases and then decreases with increase in the electron temperature. At around the peak of the SBS reflectivity, the positive frequency shift of IAW induced by electron trapping roughly offsets the negative frequency shift induced by ion trapping.

On the Formation Mechanism of Martian Dayside Ionospheric Plasma Depletion Events

AbstractPlasma Depletion Events (PDEs) are characterized by abrupt, localized reductions in ionospheric plasma density at least by an order of magnitude decrease. These events are observed over a limited range of altitudes, typically spanning a few tens of kilometers. We use Mars Atmosphere and Volatile Evolution spacecraft data to investigate the properties and possible formation mechanism of daytime PDEs, typically observed at altitudes above 250 km. We show, using two example events and statistical analysis, that the depletion events are associated with electrostatic fluctuations and increased electron temperatures. The events are further accompanied by enhanced fluxes of suprathermal electrons and light energetic ions. These are indicative of local plasma heating, possibly mediated by the electrostatic fluctuations. The heated plasma may eventually escape from the depletion region through the ambipolar diffusion.

Microscopic structure of electromagnetic whistler wave damping by kinetic mechanisms in hot magnetized Vlasov plasmas

Electromagnetic transverse perturbations propagating parallel to the external magnetic field in a warm electron plasma, specifically the warm electron whistler-mode waves, are simulated in Maxwellian as well as κ distributed (with energetic tail) electrons. The Vlasov-Maxwell phase-space continuum simulations are applied to the stable and unstable (i.e. isotropic and anisotropic) VDFs. The variation of real frequency from both numerical solution of dispersion relation and simulations show limited sensitivity to electron temperature in low wave-number regime as compared to high wave number regime, however the opposite holds for the imaginary frequency or the decay rate. The analytically predicted reduction in the decay rate of the whistler-mode with increasing electron temperature is recovered by the Vlasov-Maxwell simulations. The phase-space portraits of the these cases show that after the linear damping phase of the evolution, the particles are trapped in the wave magnetic field leading to the wave amplitudes oscillating about a mean value which follow the theoretical analysis. Palmadesso and Schmidt (1971) Physics of Fluids 14, 1411.

4f electron temperature driven ultrafast electron localization

Valence transitions in strongly correlated electron systems are caused by orbital hybridization and Coulomb interactions between localized and delocalized electrons. The transition can be triggered by changes in the electronic structure and is sensitive to temperature variations, applications of magnetic fields, and physical or chemical pressure. Launching the transition by photoelectric fields can directly excite the electronic states and thus provides an ideal platform to study the correlation among electrons on ultrafast timescales. The EuNi2(Si0.21Ge0.79)2 mixed-valence metal is an ideal material to investigate the valence transition of the Eu ions via the amplified orbital hybridization by the photoelectric field on subpicosecond timescales. A direct view on the 4f electron occupancy of the Eu ions is required to understand the microscopic origin of the transition. Here we probe the 4f electron states of EuNi2(Si0.21Ge0.79)2 at the sub-ps timescale after photoexcitation by x-ray absorption spectroscopy across the Eu M5-absorption edge. The observed spectral changes due to the excitation indicate a population change of total angular momentum multiplet states J = 0, 1, 2, and 3 of Eu3+ and the Eu2+ J = 7/2 multiplet state caused by an increase in 4f electron temperature that results in a 4f localization process. This electronic temperature increases combined with fluence-dependent screening accounts for the strongly nonlinear effective valence change. The data allow us to extract a time-dependent determination of an effective temperature of the 4f shell, which is also of great relevance in the understanding of metallic systems' properties, such as the ultrafast demagnetization of ferromagnetic rare-earth intermetallic and their all-optical magnetization switching. In addition, our results elucidate the energetics of charge fluctuations in valence-mixed electronic systems, which provide enriched knowledge regarding the role of valence transitions and orbital hybridization for quantum critical phenomena. Published by the American Physical Society 2024

Acceleration mechanisms of energetic ion debris in laser-driven tin plasma EUV sources

Laser-driven tin plasmas are driving new-generation nanolithography as sources of extreme ultraviolet (EUV) radiation centered at 13.5 nm. A major challenge facing industrial EUV source development is predicting energetic ion debris produced during the plasma expansion that may damage the sensitive EUV channeling multilayer optics. Gaining a detailed understanding of the plasma dynamics and ion acceleration mechanisms in these sources could provide critical insights for designing debris mitigation strategies in future high-power EUV sources. We develop a fully kinetic model of tin-EUV sources using one-dimensional particle-in-cell simulations to study ion debris acceleration, which will be valuable for cross-validation of radiation-hydrodynamic simulations. An inverse-bremsstrahlung heating operator is used to model the interaction of a tin target with an Nd:YAG laser, and thermal conduction is included through a Monte Carlo Coulomb collision operator. While the large-scale evolution is in reasonable agreement with analogous hydrodynamic simulations, the significant timescale for collisional equilibration between electrons and ions allows for the development of prominent two-temperature features. A collimated flow of energetic ions is produced with a spectrum that is significantly enhanced at high energies compared to fluid simulations. The dominant acceleration mechanism is found to be a large-scale electric field supported mainly by the electron pressure gradient, which is enhanced in the kinetic simulations due to the increased electron temperature. We discuss the implications of these results for future modeling of tin-EUV sources and the development of debris mitigation schemes.

The dynamical behavior of the capacitively coupled argon plasma driven by very high frequency

The dynamical behavior of the capacitively coupled Ar plasma driven by four frequencies (54, 80, 94 and 100[Formula: see text]MHz) at fixed pressure are simulated by the particle-in-cell/Monte-Carlo collisions (PIC/MCC) model based on the electromagnetic field. The magnetic field is generated by plasma current itself. The results show that the electron density, charge density, and electron temperature increase with the frequency increase when radio frequency (RF) power is 40[Formula: see text]W. The electron heating rate and argon ion heating rate near the sheath increase with the frequency increase. The high-energy electron density ([Formula: see text] [Formula: see text]eV) varies nonlinearly with the frequency increase. The high-energy electron density is highest at 80[Formula: see text]MHz among the four frequencies. The electron density, charge density, and high-energy electron density increase with RF power (30, 45, 60, and 75[Formula: see text]W) increase at 80[Formula: see text]MHz. The electron temperature decreases with RF power increase at 80[Formula: see text]MHz. The electron heating rate and argon ion heating rate near the sheath have no change with RF power increase at 80[Formula: see text]MHz. The electron energy probability distributions (EEPF) show that the number of high-energy electrons ([Formula: see text] [Formula: see text]eV) is highest at 80[Formula: see text]MHz. The reason may be the electron resonant heating that occurs in the plasma when the electron cyclotron frequency equals source frequency at 80[Formula: see text]MHz. The electron dynamics of capacitively coupled plasma is important for microelectronics etching and membrane deposition.

Ultrafast All‐Optical Control of Light Chirality with Nanostructured Graphene

AbstractUltrafast nanophotonics is a rapidly growing area of study focused on creating nanodevices that can modulate the properties of light at, to this date, unparalleled speed. To facilitate the growth of this field, there is a growing need for compact metamaterial designs for the manipulation of the amplitude, phase, and polarization of light. One promising strategy involves leveraging the optical nonlinearity of nanostructured materials to alter their permittivity by interacting with high‐intensity ultrashort laser pulses. This study showcases how such requirements can be met through the utilization of 2D materials, particularly graphene. The nonlinear optical response of a graphene nanorectangle array is theoretically modeled to achieve all‐optical, fully reversible, broadband, and ultrafast dynamic control of light chirality. This is achieved by taking advantage of the energy relaxation dynamics of coherently excited localized plasmons supported by the metasurface, and the transient increase in electron temperature in graphene. Using finite‐difference time‐domain simulations, ultrafast dynamic tuning between circular and linearly polarized light is demonstrated. The proposed platform gives promise for ultrathin, CMOS‐compatible nanophotonic systems that can provide high‐speed, room‐temperature modulation of light polarization.

Spectral Analysis of Al Arc Discharge Plasma Generated in ZnO/DDDW Colloid

This study aims to investigate the aluminum (Al) arc plasma parameters generated through the explosive strip technique. The research involves the measurement of key plasma characteristics such as plasma frequency (fp), Debye length, and Debye number. The electron temperature (Te) and electron density (ne) of the plasma were calculated utilizing the Boltzmann plot and Stark expansion method. Analysis of the optical emission spectrum revealed distinctive peaks corresponding to oxygen, Al, and zinc oxide (ZnO) within the plasma. The outcomes of the study demonstrated a noteworthy correlation between the applied current and the electron temperature and density. Specifically, as the current increases, both electron temperature and density increase. The electron temperature of the Al plasma increased from the range of 0.852 eV to 0.92404 eV, accompanied by a corresponding elevation in electron density from 13.1× 1017 cm-3 to 15.2× 1017 cm-3. Furthermore, the detonation of the Al strip within a ZnO suspension led to even more pronounced changes. In this case, the electron temperature surged from 0.92885 eV to 1.1012 eV, and the electron density experienced an increase from 37.7 × 1017 cm-3 to 44.7 × 1017 cm-3.