Electron Energy Dissipation Research Articles

Statistical Study of the Sub-ion-scale Magnetic Holes in the Lunar Space Environment

Sub-ion-scale magnetic holes play a significant role in electron transportation and energy dissipation. In the upstream region of the terrestrial bow shock, they are expected to originate from the upstream solar wind as well as the foreshock. The Moon can move into the solar wind; whether it can affect the observation of the sub-ion-scale magnetic holes is unclear. Here, we statistically investigate 268 sub-ion-scale magnetic holes in the lunar space environment based on observations of the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun mission. The median duration of these magnetic holes is ∼0.31 s, and the median size of their cross sections is ∼0.5 ρ i or ∼38.9 ρ e. We regard an isolated or a train of magnetic holes as an event; thus, these magnetic holes belong to 207 events. The data at X SSE < 0 and |Y SSE| < 2 R M (lunar radii) account for ∼21.7% of all observed data, but ∼89.4% of the events are observed in this region, suggesting that they are more likely to occur in the lunar wake. Furthermore, their occurrence rates in the lunar wake are much larger in the region close to its boundary than in other wake regions. And the occurrence rates in the lunar wake near the boundary at X SSE > −3 R M are larger in the dawnside than that in the duskside. These observations suggest that the region in the lunar wake close to its boundary is a possible source of sub-ion-scale magnetic holes.

Energy Dissipation of Fast Electrons in Polymethylmethacrylate: Toward a Universal Curve for Electron-Beam Attenuation in Solids between ∼0 eV and Relativistic Energies.

Spectroscopy of correlated electron pairs was employed to investigate the energy dissipation process, as well as the transport and the emission of low-energy electrons on a polymethylmethacrylate surface, providing secondary electron spectra causally related to the energy loss of the primary. Two groups are identified in the cascade of slow electrons, corresponding to different stages in the energy dissipation process. The characteristic lengths for attenuation due to collective excitations and momentum relaxation are quantified for both groups and are found to be distinctly different: λ_{1}=(12±2) Å and λ_{2}=(62±11) Å. The results strongly contradict the commonly employed model of exponential attenuation with the electron inelastic mean free path as characteristic length, but they essentially agree with a theory used for decades in astrophysics and neutron transport, albeit with characteristic lengths expressed in units of angstroms rather than light-years.

Time-dependent electron transfer and energy dissipation in condensed media.

We study a moving adsorbate interacting with a metal electrode immersed in a solvent using the time-dependent Newns-Anderson-Schmickler model Hamiltonian. We have adopted a semiclassical trajectory treatment of the adsorbate to discuss the electron and energy transfers that occur between the adsorbate and the electrode. Using Keldysh Green's function scheme, we found a non-adiabatically suppressed electron transfer caused by the motion of the adsorbate and coupling with bath phonons that model the solvent. The energy is thus dissipated into electron-hole pair excitations, which are hindered by interacting with the solvent modes and facilitated by the applied electrode potential. The average energy transfer rate is discussed in terms of the electron friction coefficient and given an analytical expression in the slow-motion limit.

Modulation mechanism of electron energy dissipation on superlubricity based on fluorinated 2D ZIFs

Modulation mechanism of electron energy dissipation on superlubricity based on fluorinated 2D ZIFs

Electron energy dissipation in a magnetotail reconnection region

The four Magnetospheric Multiscale spacecraft encountered a reconnection region in the Earth's magnetospheric tail on 11 July 2017. Previous publications have reported characteristics of the electron diffusion region, including its aspect ratio, the reconnection electric field, plasma wave generation from electron beams in its vicinity, and energetic particles in the Earthward exhaust. This paper reports on the investigation of conversion of electromagnetic energy to electron kinetic energy (by J·E) and the ensuing conversion of electron beam energy to electron thermal energy via the pressure–strain interaction. The main result is that omnidirectional, compressive dissipation of electron energy dominates in the positive J·E region, while incompressive parallel dissipation dominates in the inflow region where J·E is small. The existence of parallel electric fields in the inflow region supports previous suggestions that electron trapping by these fields contributes to the parallel dissipation. All of the results are reproduced quantitatively within a factor of two with a 2.5-D particle-in-cell simulation.

The high-light-induced protein SliP4 binds to NDH1 and photosystems facilitating cyclic electron transport and state transition in Synechocystis sp. PCC 6803.

An increasing number of small proteins has been identified in the genomes of well-annotated organisms, including the model cyanobacterium Synechocystis sp. PCC 6803. We describe a newly assigned protein comprising 37 amino acids that is encoded upstream of the superoxide dismutase SodB encoding gene. To clarify the role of SliP4, we analyzed a Synechocystis sliP4 mutant and a strain containing a fully active, Flag-tagged variant of SliP4 (SliP4.f). The initial hypothesis that this small protein might be functionally related to SodB could not be supported. Instead, we provide evidence that it fulfills important functions related to the organization of photosynthetic complexes. Therefore, we named it a small light-induced protein of 4 kDa, SliP4. This protein is strongly induced under high-light conditions. The lack of SliP4 causes a light-sensitive phenotype due to impaired cyclic electron flow and state transitions. Interestingly, SliP4.f was co-isolated with NDH1 complex and both photosystems. The interaction between SliP4.f and all three types of complexes was further confirmed by additional pulldowns and 2D-electrophoreses. We propose that the dimeric SliP4 serves as a molecular glue promoting the aggregation of thylakoid complexes, which contributes to different electron transfer modes and energy dissipation under stress conditions.

Langmuir waves associated with magnetic holes in the solar wind

Context.Langmuir waves (electrostatic waves near the electron plasma frequency) are often observed in the solar wind and may play a role in the energy dissipation of electrons. The largest amplitude Langmuir waves are typically associated with type II and III solar radio bursts and planetary foreshocks. In addition, Langmuir waves not related to radio bursts occur in the solar wind, but their source is not well understood. Langmuir waves have been observed inside isolated magnetic holes, suggesting that magnetic holes play an important role in the generation of Langmuir waves.Aims.We provide the statistical distribution of Langmuir waves in the solar wind at different heliocentric distances. In particular, we investigate the relationship between magnetic holes and Langmuir waves. We identify possible source regions of Langmuir waves in the solar wind, other than radio bursts, by analyzing the local plasma conditions.Methods.We analyzed data from Solar Orbiter’s Radio and Plasma Waves (RPW) and Magnetometer (MAG) instruments. We used the triggered electric field snapshots and onboard statistical data (STAT) of the Time Domain Sampler (TDS) of RPW to identify Langmuir waves and investigate their properties. The plasma densities were derived from the spacecraft potential estimated by RPW. The MAG data were used to monitor the background magnetic field and detect magnetic holes, which are defined as regions with an isolated decrease in |B| of 50% or more compared to the background level. The statistical analysis was performed on data from 2020 to 2021, comprising heliocentric distances between 0.5 AU and 1 AU.Results.We show that 78% of the Langmuir waves in the solar wind not connected to radio bursts occur in regions of local magnetic field depletions, including the regions classified as isolated magnetic holes. We also show that the Langmuir waves occur more frequently inside magnetic holes than in any other region in the solar wind, which indicates that magnetic holes are important source regions of solar wind Langmuir waves. We find that Langmuir waves associated with magnetic holes in the solar wind typically have lower amplitudes than those associated with radio bursts.

Hysteresis light curves: a protocol for characterizing the time dependence of the light response of photosynthesis.

Photosynthesis vs. light curves (LCs) have played a central role in photosynthesis research for decades. They are the commonest form of describing how photosynthesis responds to changes in light, being frequently used for characterizing photoacclimation. However, LCs are often interpreted exclusively regarding the response to light intensity, the effects of time of exposure not being explicitly considered. This study proposes the use of 'hysteresis light curves' (HLC), an experimental protocol focused on the cumulative effects of light exposure to obtain information on the time dependence of photosynthetic light responses. HLC are generated by exposing samples to a symmetrical sequence of increasing and decreasing light levels. The comparison of the light-increasing and the light-decreasing phases allows the quantification of the hysteresis caused by high-light exposure, the magnitude and direction of which inform on the activation, and subsequent relaxation of high-light-induced photosynthetic processes. HLCs of the chlorophyll fluorescence indices rETR (relative electron transport rate of photosystem II) and Y(NPQ) (index of non-photochemical quenching) were measured on cyanobacteria, algae, and plants, with the aim of identifying main patterns of hysteresis and their diversity. A non-parametric index is proposed to quantify the magnitude and direction of hysteresis in HLCs of rETR and Y(NPQ). The results of this study show that HLCs can provide additional relevant information on the time dependence of the light response of photosynthetic samples, not obtainable from conventional LCs, useful for phenotyping photosynthetic traits, including photoacclimation state and kinetics of light activation and relaxation of electron flow and energy dissipation processes.

Magnetospheric Multiscale Mission Observations of Lower-hybrid Drift Waves in Terrestrial Magnetotail Reconnection with Moderate Guide Field and Asymmetric Plasma Density

Utilizing high-resolution data from the Magnetospheric Multiscale mission, we present new observations of lower-hybrid drift waves (LHDWs) in terrestrial magnetotail reconnection with guide field levels of ∼70% and asymmetric plasma density (N high/N low ∼ 2.5). The LHDWs, driven by lower-hybrid drift instability, were observed in correlation with magnetic field and density gradients at separatrices on both sides of the reconnection current sheet. The properties of the LHDWs at both sides of the separatrices are different: (1) At high-density side separatrices, the LHDWs with wavelength kρ e ∼ 0.41 propagated away from the X-line mainly in the L–M plane; (2) at the low-density side separatrices, the LHDWs with wavelengths kρ e ∼ 0.76 and kρ e ∼ 0.35 propagated mainly along the outflow direction and current sheet normal. It is also found that the perpendicular magnetic field fluctuations were comparable to the parallel component. Wave potential of the LHDWs was 20% ∼ 35% of the electron temperature. The LHDWs contributed to electron demagnetization and energy dissipation. Our study can promote understanding of properties of LHDWs during magnetic reconnection.

Irradiation-induced microstructural transformations in UO2 accelerated upon electronic energy deposition

The combination of electronic and nuclear energy deposition can have an effect on the defect production and evolution that is not simply the sum of both independent contributions. In nuclear reactors, the fuel is exposed to the irradiation of several particles such as the fission fragments (FF) whose electronic to nuclear energy loss ratio evolves along their path. To understand the impact of this energy-loss coupling on the fuel microstructure, single and dual-beam ion irradiations of uranium dioxide (UO2) were carried out. The damage evolution was investigated by Raman spectroscopy analysis correlated with Transmission Electronic Microscopy observations. It was found a significant acceleration effect of the electronic energy dissipation on the formation and evolution of defects induced by the nuclear energy deposition. The magnitude of this acceleration was shown to depend on both the electronic energy loss level and the microstructure at the moment when the coupling occurs.

Electronic stopping power and electronic energy-loss mechanism for a low-energy ion in TiN under channeling conditions

The electronic stopping power of a low-energy proton in a crystalline TiN film is investigated by computer simulation based on the time-dependent density-functional theory. The calculated results show that the electronic stopping power of the small impact parameter coincides with the experimental data. By evaluating the channeling electronic density and the stopping force in different channels, the direction dependence of the electronic stopping power is explored and revealed. Along the $\ensuremath{\langle}110\ensuremath{\rangle}$ channel, the electronic stopping power of the proton is lower than that of the $\ensuremath{\langle}100\ensuremath{\rangle}$ and $\ensuremath{\langle}111\ensuremath{\rangle}$ channels; this trend is mainly attributed to the discrepancy in the channeling electronic density. In addition, our research gives evidence that the threshold velocity ${v}_{th}=0.1294\phantom{\rule{0.16em}{0ex}}\text{a.u.}$ is closely related to the indirect band gap. That result suggests that only the valence band's electrons across the band gap can contribute to the electronic energy dissipation; therefore, we discuss that the defect state induced in the gap by the passing ion serves like an elevator ferrying the valence-band electrons across the indirect band gap. Last, we investigate the charge accumulation and depletion as an energy-loss model by intuitive charge-density difference. Furthermore, the intensity of the chemical bond between the projectile and the host atoms around the channel is indirectly investigated and analyzed by obtaining the amplitude of the electron localization function. The shortening and elongation of the chemical bond are deemed a mechanism of the electronic energy loss in the process of the ion-solid interaction, which can contribute to the electronic stopping power. These results supply reference data for the application of the excellent material TiN in ion-beam irradiation.

Role of electronic energy loss on defect production and interface stability: Comparison between ceramic materials and high-entropy alloys

High-entropy alloys (HEAs) and some complex alloys exhibit desirable properties and significant structural stability in harsh environments, including possible applications in advanced reactors. Energetic ion irradiation is often used as a surrogate for neutron irradiation; however, the impact of ion electronic energy deposition and dissipation is often neglected. Moreover, differences in recoil energy spectrum and density of cascade events on damage evolution must also be considered. In many chemically complex alloys, the mean free path of electrons is reduced significantly, thus their decreased thermal conductivity and slow dissipation of localized radiation energy can have noticeable effects on displacement cascade evolution that is greatly different from metals with high thermal conductivity. In this work, nanocrystalline HEAs of Ni20Fe20Co20Cr20Cu20 and nonequiatomic (NiFeCoCr)97Cu3, both having much lower room-temperature thermal conductivity than pure Ni or Fe, are chosen as model HEAs to reveal the role that electronic energy loss during ion irradiation has in complex alloys. The response of nanocrystalline HEAs is investigated under irradiation at room temperature using MeV Ni and Au ions that have different ratios of electronic energy to damage energy, which is the energy dissipated in displacing atoms. Different from previously reported amorphization of nanocrystalline SiC, experimental results on these HEAs show that, similar to the process in nanocrystalline oxide materials, both inelastic thermal spikes via electron–phonon coupling and elastic thermal spikes via collisions among atomic nuclei contribute to the overall grain growth. The growth follows a power law dependence with the total deposited ion energy, and the derived value of the power-exponent suggests that the irradiation-induced instability at and near grain boundaries leads to local rapid atomic rearrangements and consequently grain growth. The high power-exponent value can be attributed to the sluggish diffusion and delayed defect evolution arising from the chemical complexity intrinsic to HEAs. This work calls attention to quantified fundamental understanding of radiation damage processes beyond that of simplified displacement events, especially in simulating neutron environments.

Simulation of Ab Initio Optical Absorption Spectrum of β-Carotene with Fully Resolved S0 and S2 Vibrational Normal Modes.

The electronic absorption spectrum of β-carotene (β-Car) is studied using quantum chemistry and quantum dynamics simulations. Vibrational normal modes were computed in optimized geometries of the electronic ground state S0 and the optically bright excited S2 state using the time-dependent density functional theory. By expressing the S2-state normal modes in terms of the ground-state modes, we find that no one-to-one correspondence between the ground- and excited-state vibrational modes exists. Using the ab initio results, we simulated the β-Car absorption spectrum with all 282 vibrational modes in a model solvent at 300 K using the time-dependent Dirac-Frenkel variational principle and are able to qualitatively reproduce the full absorption line shape. By comparing the 282-mode model with the prominent 2-mode model, widely used to interpret carotenoid experiments, we find that the full 282-mode model better describes the high-frequency progression of carotenoid absorption spectra; hence, vibrational modes become highly mixed during the S0 → S2 optical excitation. The obtained results suggest that electronic energy dissipation is mediated by numerous vibrational modes.

In Situ Detection of Kinetic-size Magnetic Holes in the Martian Magnetosheath

Abstract Depression in magnetic field strength with a scale below one proton gyroradius is referred to as a kinetic-size magnetic hole (KSMH). KSMHs are frequently observed near Earth’s space environments and are thought to play an important role in electron energization and energy dissipation in space plasmas. Recently, KSMHs have been evidenced in the Venusian magnetosheath. However, observations of KSMHs in other planetary environments are still lacking. In this study, we present the in situ detection of KSMHs in the Martian magnetosheath using Mars Atmosphere and Volatile EvolutioN (MAVEN) for the first time. The distribution of KSMHs is asymmetry in the southern–northern hemisphere and no obvious asymmetry in the dawn–dusk hemisphere. The observed KSMHs are accompanied by increases in the electron fluxes in the perpendicular direction, indicating the cues of trapped electrons and the formation of electron vortices inside KSMHs. These features are similar to the observations in the Earth’s magnetosheath and magnetotail plasma sheet and the Venusian magnetosheath. This implies that KSMHs are a universal magnetic structure in space.

Momentum and energy dissipation of hot electrons in a Pb/Ag(111) quantum well system

The band structure of multilayer systems plays a crucial role for the ultrafast hot carrier dynamics at interfaces. Here, we study the energy- and momentum-dependent quasiparticle lifetimes of excited electrons in a highly ordered Pb monolayer film on Ag(111) prior and after the adsorption of a monolayer of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA). Using time-resolved two-photon momentum microscopy with femtosecond visible light pulses, we show that the electron dynamics of the Pb/Ag(111) quantum well system is largely dominated by two types of scattering processes: (i) isotropic intraband scattering processes within the quantum well state (QWS) and (ii) isotropic interband scattering processes from the ${p}_{z}$-like QWS into the Pb ${p}_{x/y}$ band. In the latter case, the Pb QWS acts as an electron source for the momentum space refilling process of the Pb ${p}_{x/y}$ band. This conclusion is confirmed by the modification of the band structure and the quasiparticle dynamics of the Pb/Ag(111) bilayer film after the adsorption of PTCDA. We find both an adsorption-induced suppression of the QWS itself as well as of the refilling process into the Pb ${p}_{x/y}$ band. Our study hence demonstrates the isotropic nature of the momentum-dependent scattering processes of metallic bilayer systems and uncovers a new possibility to selectively tune and control scattering processes occurring in quantum (well) materials by the adsorption of organic molecules.

Deterministic particle assembly on nanophotonic chips

HypothesisControlled particle assembly from a dilute suspension droplet is challenging yet important for many lab-on-a-chip and biosensing applications. The formation of hot spots on the localized surface plasmonic resonance (LSPR) substrates induced by laser excitation can generate microbubbles. These microbubbles, upon the laser removal, shrink and collapse due to electron energy dissipation, leading to guided particle assembly on the LSPR substrate. ExperimentsAfter depositing dilute silica particles dispersions on both nanoisland (AuNI) and planar gold (Au) plasmonic substrates (referred to as LSPR and SPR substrates respectively), microbubbles were formed when a laser beam was applied. Particle dispersion concentration, laser power, and the radius of circular laser sequence were varied to produce different sizes of particle clusters on the LSPR substrate after bubble shrinkage upon the laser removal. To stabilize the assembled structures over time, sodium chloride (NaCl) was ad ded to the dispersions. FindingsEven though thermo-plasmonic flow and microbubbles can be produced with SPR substrates, particle assembly is only possible on LSPR substrates because of electron energy dissipation via nanoscale air gaps trapped in the LSPR substrate. By tuning the laser power, the radius of the circular laser sequence, and the particle dispersion concentration, the number of particles in the assembled structure can be controlled. The addition of NaCl to the dispersion can screen the electrostatic charges among the particles and between the particles and substrate, favoring hydrogen bonding and stabilizing the assembled structures for hours. These findings establish a new framework for utilizing nanophotonic chips where particle assembly can be achieved by a single source of light.

Analysis of the chemical network in a volume-production high-current negative hydrogen ion source

Complex simulations (e.g. multi-dimensional fluid models) usually prevent the use of very large chemistry models. In this work, the important physicochemical processes in a volume-production high-current negative hydrogen ion source (HCNHIS) are identified for a pressure range of 1–100 Torr using a global model. The particle species include H2(υ = 0–14), H(n = 1–3), , , H+, H−, and electrons. The simulation results indicate that for the production of negative hydrogen ions through dissociative attachments, the high vibrational levels of hydrogen molecules are important at low pressures, and the ground state and low vibrational levels of hydrogen molecules play an increasingly important role with increasing pressure. The reactions involving the ground state, low vibrational levels, and neighboring levels of each level tend to dominate the production of vibrational levels and transitions between them in the volume-production HCNHIS. With increasing pressure, the electron energy dissipation shifts from dissociation of H2(υ = 0) and electron excitation of H2(υ = 0) through an indirect mechanism followed by radiative decay (the EV process) to electron excitation of H2(υ = 0) through a resonant mechanism (the eV process). A valuable subset of reactions provided by the simplified model is proposed in the investigated pressure range, which could be incorporated in more complex simulations. The results obtained with the simplified model under different simulation conditions are within an acceptable error margin of the results for the full model, which indicates that the robustness of the simplified model of chemical reactions is guaranteed to some extent.

Synergistic effects assessment between nuclear damage and electronic energy dissipation in LiTaO3 under heavy ion irradiation using optical waveguides properties and the irradiation angle of incidence

High energy heavy ion irradiation has been performed in LiTaO3 in a broad set of experimental conditions to study the synergistic effects in the damage generation between the nuclear and the electronic energy loss mechanisms. Optical waveguides have been fabricated in LiTaO3, using 20–25 MeV F and 40 MeV Si ions, and their refractive index profiles were used as a very accurate method for the in-depth damage profile determination and its correlation with the energy loss curves. In-situ optical reflectance of low energy irradiations (500 keV F and 300 keV Si ions) has been performed to estimate the nuclear damage kinetics of the buried regions of the high energy irradiations that are not optically accessible with the optical waveguide characterization in the fluence regime when the electronic damage is intense. The angle of incidence has been varied to enhance the damage and further ascertain the existence of a synergistic mechanism.

Desaturated EUV Flare Ribbons in an X-class Flare

Abstract This paper studies the energy dissipation of nonthermal electrons in the chromospheric flare ribbons during the peak time of a Geostationary Operational Environmental Satellite X-class flare (SOL2011-09-06) using desaturated Solar Dynamics Observatory/Atmospheric Imaging Assembly extreme-ultraviolet (EUV) narrow-band images. The temperature distribution in emission measure, called the differential emission measure (DEM), derived from the EUV fluxes from the flare ribbons shows an increase in the emission measure up to a temperature around 9 × 106 K, followed by a steep decline at higher temperatures. In contrast, the flare loop reaches temperatures up to 27 × 106 K. This result is in agreement with previously reported single-temperature measurements using soft X-ray filter images, as well as DEM distributions reported for smaller flares obtained from EUV line observations. The main difference between small and large flares appears to be an increased emission measure in the flare ribbons, while the ribbon peak temperature is similar for all flares. This is different from the flare loop temperatures, where the hottest temperatures occur in the largest flares. However, the physically relevant quantity for energy dissipation, the energy content of the heated plasma as a function of temperature, does not need to peak at the same temperature as the DEM. The poorly constrained source thickness in radial extent of the flare ribbons has a significant impact on the shape of the differential thermal energy distribution. In particular, if the highest temperatures occur over a wide radial extent as “evaporating” plasma starts expending, the largest amount of energy could potentially be hidden above the peak temperature of the DEM.

Effects of recoil spectra and electronic energy dissipation on defect survival in 3C-SiC

The coincidence of electronic and damage energy dissipation from energetic ions to an atomic lattice can significantly affect damage production along the ion trajectory due to spatial overlap of inelastic and elastic processes. Damage production and disordering in single crystal 3C-SiC from 5 MeV Si and 10 MeV Au ions is investigated using ion-channeling experiments. While defects are created by damage energy dissipation via elastic scattering, electronic energy dissipation via electron-phonon coupling decreases defect survival along the ion trajectory for Si ions. The more energetic recoil spectrum for 10 MeV Au ions leads to weaker spatial coupling of electronic and damage energy dissipation processes, and damage production is only weakly affected.