External Static Electric Field Research Articles

Glory interference spectroscopy in Sr atom

Slow (meV) photoelectron imaging spectroscopy is employed in the experimental study of near-threshold photoionization of strontium atoms in the presence of an external static electric field. Specifically, the study is devoted to the glory effect, that is, the appearance of an intense peak at the center of the recorded photoelectron images, when dealing with m= 0 final ionized Stark states (m denoting the magnetic quantum number). This critical effect is formally identical to that encountered in classical scattering theory, where, for a nonzero value of the impact parameter, the zero-crossing of the deflection function leads to a divergent classical differential cross section. By recording the magnitude variation of this glory peak as a function of electron excitation energy, we observe that, besides the traces of classical origin, it also exhibits intense quantum interference and beating phenomena, above and below the zero-static-field ionization threshold. We study both, single- and two-photon ionization of Sr, thus enabling a comparison not only between the different excitation schemes, but also with an earlier work devoted to two-photon ionization of Mg atom by Kalaitzis et al (2020 Phys. Rev. A 102 033101). Our recordings are analyzed within the framework of the Harmin–Fano frame transformation Stark effect theory that is applied to both the hydrogen atom and a non-hydrogenic one simulating Sr. We discuss the various aspects of the recorded and calculated glory interference and beating structures and their ‘short time Fourier transforms’ and classify them as either atom-specific or atom independent. In particular, we verify the ‘universal’ connection between the glory oscillations above the zero-field threshold and the differences between the origin-to-detector times of flight corresponding to pairs of classical electron trajectories that end up to the image center.

DFT-D3 and TD-DFT Studies of the Adsorption and Sensing Behavior of Mn-Phthalocyanine toward NH3, PH3, and AsH3 Molecules.

This study employs density functional theory (DFT) calculations at the B3LYP/6-311+g(d,p) level to investigate the interaction of XH3 gases (X = N, P, As) with the Mn-phthalocyanine molecule (MnPc). Grimme's D3 dispersion correction is applied to consider long-range interactions. The adsorption behavior is explored under the influence of an external static electric field (EF) ranging from -0.514 to 0.514 V/Å. Chemical adsorption of XH3 molecules onto the MnPc molecule is confirmed. The adsorption results in a significant decrease in the energy gap (Eg) of MnPc, indicating the potential alteration of its optical properties. Quantum theory of atoms in molecules (QTAIM) analysis reveals partially covalent bonds between XH3 and MnPc, and the charge density differenc (Δρ) calculations suggest a charge donation-back donation mechanism. The UV-vis spectrum of MnPc experiences a blue shift upon XH3 adsorption, highlighting MnPc's potential as a naked-eye sensor for XH3 molecules. Thermodynamic calculations indicate exothermic interactions, with NH3/MnPc being the most stable complex. The stability of NH3/MnPc decreases with increasing temperature. The direction and magnitude of the applied electric field (EF) play a crucial role in determining the adsorption energy (Eads) for XH3/MnPc complexes. The Eg values decrease with an increasing negative EF, which suggests that the electrical conductivity (σ) and the electrical sensitivity (ΔEg) of the XH3/MnPc complexes are influenced by the magnitude and direction of the applied EF. Overall, this study provides valuable insights into the suggested promising prospects for the utilization of MnPc in sensing applications of XH3 gases.

Influence of a static electric field on magnetic materials monitored by X-ray magnetic circular dichroism

The magnetic circular X-ray dichroism (XMCD) in X-ray absorption spectroscopy (XAS) is extensively used to monitor the response of a magnetic system to an external perturbation. Application of a static external electric field to control its magnetic properties may just lead to a charge rearrangement or to a steady electric current dependent on the geometry. As it is demonstrated, the first situation can be handled with minor modifications of the standard well established schemes to calculate XAS and XMCD spectra. For the second case, however, more advanced schemes have to be used that account for the steady-state out-of-equilibrium situation. It is shown, that this can indeed be achieved by making use of the Keldysh non-equilibrium Green function formalism that allows in particular to express the X-ray absorption coefficient in terms of the corresponding greater Green function G>(E). As an alternative approach, a bi-linear response formalism is presented that can be used to calculate the modification of the XMCD spectra due to the electric field directly.

Tunable chiral photonic cavity based on multiferroic layers.

Realization of externally tunable chiral photonic sources and resonators is essential for studying and functionalizing chiral matter. Here, oxide-based stacks of helical multiferroic layers are shown to provide a suitable, electrically-controllable medium to efficiently trap and filter purely chiral photonic fields. Using analytical and rigorous coupled wave numerical methods we simulate the dispersion and scattering characteristics of electromagnetic waves in multiferroic heterostructures. The results evidence that due to scattering from the spin helix texture, only the modes with a particular transverse wavenumber form standing chiral waves in the cavity, whereas all other modes leak out from the resonator. An external static electric field enables a nonvolatile and energy-efficient control of the vector spin chirality associated with the oxide multilayers, which tunes the photonic chirality density in the resonator.

Beryllium oxide nano-cage as sorbent and sensor for formaldehyde gas: DFT-D3 calculations

This work introduces DFT-D3 calculations to investigate the adsorption properties of The CH2O molecule on the Be12O12 nano-cage. The DFT-D3 calculations are performed using B3LYP/6-311 g(d,p). PDOS, NBO atomic charges, charge density difference, and QTAIM analyses are achieved. The impact of solvent, external static electric field (EF), and concentration of CH2O are examined. The CH2O molecule is chemically adsorbed on the Be12O12 nano-cage. The adsorption energy (Eads) and the HOMO-LUMO gap (Eg), consequently, the sensitivity, response time, and recovery time are controlled by the type of solvent, the electric field, and the concentration of CH2O. The Eads in the vacuum is −0.947 eV while in presence of negative EF enhanced it by 15.61 %. The Eg of Be12O12 is 7.870 eV whereas it reduced due to the adsorption of CH2O to 5.029 eV, then to 4.439 eV in the presence of the negative EF and to 3.688 eV at a high concentration of CH2O. Therefore, the results suggest that the Be12O12 nano-cage is a promising sensor for formaldehyde gas.

Impact of external static electric field on surface tension of model solutions

Food foams are thermodynamically unstable systems. Their stabilization remains a challenge in the industry. To understand the interactions between an electrostatic field (SEF) and food foam, a microscopic study was conducted. Using a specially designed tensiometer, a liquid droplet (water, WPI solution, chickpea liquor) was placed between two parallel electrodes and subjected to an SEF (0 to 800 kV/m). Images of the pendant droplet were recorded throughout the experiment. Based on Laplace's equation, the surface tension was calculated as function of the applied voltage.The geometry of the droplet was deformed under SEF. The surface tension decreased proportionally to the rise of the voltage (γdistilled water=21.7.10−3 N/m at 800 kV/m).The mechanism causing surface tension reduction was found to be the electric charge existing on the liquid surface. By reducing surface tension, drops are likely to break up more easily during expansion, which improves the organoleptic qualities of the foam.

High order harmonic spectra of CO under external electrostatic field

In this work, we use Lewenstein’s theory to calculate the high order harmonic spectra of CO molecule in a linearly polarized laser field combined with an external electrostatic field. The results show that the characteristics of the high order harmonic spectra of CO molecule depend strongly on the direction of the external static electric field relative to the orientation of CO. Especially, when the direction of the external static electric field points from O to C, the plateau of the harmonic spectrum becomes wider and the cutoff frequency reaches a larger value than the scenario without external static electric field. When the direction of the external static electric field points from C to O, the harmonic spectrum shows a double-plateau structure. Using Lewenstein theory, these phenomena can be understood from the viewpoint that the harmonic generation comes from a coherent superposition of the contributions of two kinds of channels characterized by C-end ionization and O-end ionization. The C(O)-end ionization channel means that the electron is ionized from C(O) end, then accelerated by the driving electric field, finally recombines with its parent molecular ion at either C or O end, emitting the harmonics. For the same harmonic order, the contribution of the C-end ionization channel is greater than that of the the O-end ionization channel. The two kinds of channels emit harmonics in adjacent half period of laser, where the external static electric field causes the cutoff frequency of the harmonic spectrum to increase and decrease in the adjacent half period of the laser field. Especially, when the direction of external static electric field is from the C to O, the cutoff frequency of the harmonic spectrum of the C-end ionization channel decreases, resulting in a higher first plateau in the spectrum. While, the increase of cut-off frequency of the O-end ionization channel will result in a lower second plateau. When the direction of external static electric field is reversed, the cutoff frequency of the harmonics of the C-end channel increases, leading the plateau of CO harmonic spectrum to become wider than that without the external static electric field. The cut-off frequency of the O-end ionization channel decreases. Because the contribution of the O-end ionization channel can be ignored compared with that of C-end ionization channel, the C-end channel dominates the contribution to harmonic generation and hence there is only one plateau in the harmonic spectrum. This work provides a clear physical picture for the formation of a double-plateau structure of CO harmonic spectra under the action of an external static electric field.

Erratum to “Phase Separation of Polymer Blends Induced by an External Static Electric Field”

Erratum to “Phase Separation of Polymer Blends Induced by an External Static Electric Field”

Phase Separation of Polymer Blends Induced by an External Static Electric Field

Phase Separation of Polymer Blends Induced by an External Static Electric Field

Generation of adiabatic pulses

A two-dimensional GaAs/AlGaAs quantum disk under the influence of a non-central potential resulting in azimuthal distortion, subjected to an external static electric field, is exposed to a linearly polarized laser pulse. Adiabatic magnetic pulses are found to be generated due to the introduction of distortion in the system. The magnitude of distortion is expected to serve as one of the crucial control parameters for the manipulation of the generated magnetic pulses. The production of desired magnetic pulses may prove beneficial in many bio-medical applications. • A distorted GaAs/AlGaAs quantum disk is exposed to sub-picosecond laser pulse. • Non-zero radial charge currents in addition to the azimuthal components are observed. • Optimized laser parameters are found to generate pure adiabatic magnetic pulses. • These photo-induced pulses are much prominent in case of finite azimuthal distortion. • Such magnetic pulses may prove beneficial for various bio-medical applications.

Effect of nuclear charge on laser-induced fusion enhancement in advanced fusion fuels

Based on the preliminary work done in a previous paper [Phys. Rev. C 105, 054001 (2022)], we investigate the effects of laser-induced fusion rate enhancements of different fusion fuels. In the aforementioned work, which considered $_{1}^{2}\mathrm{H}\text{\ensuremath{-}}_{1}^{3}\mathrm{H}$ (D-T) and ${\mathrm{DHe}}^{3}$ fusion, it was observed that a larger product of charge numbers of the fusion reactants leads to an increased laser-induced enhancement to the fusion cross section for static external electric fields. We investigate whether this trend persists for DT, ${\mathrm{DHe}}^{3}$, and ${p\mathrm{B}}^{11}$ fusion for dynamical electric fields, using the semiclassical approaches of the Wentzel-Kramers-Brillouin method and the imaginary-time method, as well as the Kramers-Henneberger method, and the Volkoff-state approximation. We find that the fusion cross section of ${p\mathrm{B}}^{11}$ indeed exhibits the largest relative enhancement for all laser parameters considered and may even surpass the cross section of DT and ${\mathrm{DHe}}^{3}$ fusion.

Mott Insulator Ca2RuO4 under External Electric Field.

We have investigated the structural, electronic and magnetic properties of the Mott insulator Ca2RuO4 under the application of a static external electric field in two regimes: bulk systems at small fields and thin films at large electric fields. Ca2RuO4 presents S- and L-Pbca phases with short and long c lattice constants and with large and small band gaps, respectively. Using density functional perturbation theory, we have calculated the Born effective charges as response functions. Once we break the inversion symmetry by off-centering the Ru atoms, we calculate the piezoelectric properties of the system that suggest an elongation of the system under an electric field. Finally, we investigated a four-unit cell slab in larger electric fields, and we found insulator–metal transitions induced by the electric field. By looking at the local density of states, we have found that the gap gets closed on surface layers while the rest of the sample is insulating. Correlated to the electric-field-driven gap closure, there is an increase in the lattice constant c. Regarding the magnetic properties, we have identified two phase transitions in the magnetic moments with one surface that gets completely demagnetized at the largest field investigated. In all cases, the static electric field increases the lattice constant c and reduces the band gap of Ca2RuO4, playing a role in the competition between the L-phase and the S-phase.

Applicability of semiclassical methods for modeling laser-enhanced fusion rates in a realistic setting

In the context of the potential laser-induced enhancement to the rates of ${\mathrm{DHe}}^{3}$ and DT fusion, we discuss the frequently-used Wentzel-Kramers-Brillouin (WKB) method and the imaginary-time method (ITM). For static external electric fields, we find that these methods predict significant enhancement to the fusion cross section for electric-field strengths $>{10}^{14}$ V/m, especially at low values ($\ensuremath{\approx}$ keV) for the enter-of-mass (CoM) energy. When considering dynamic electric fields, this enhancement can be amplified by considering increased photon frequencies. However, we also provide a review of the region of laser-parameter phase space where these semiclassical methods are applicable. We conclude that this allowable region decreases for higher photon frequencies in conjunction with lower values for the electric-field strength, motivating the need for future experiments to test the predictions of these methods and their ranges of validity.

High Harmonic Generation from Oriented Asymmetric Molecules in the Presence of Static Electric Field

Abstract We investigate the high harmonic generation during the interaction of the femtosecond laser field with oriented asymmetric diatomic molecules in the presence of an external static electric field. Based on the numerical solution of the time-dependent Schrödinger equation for the model one-electron system, we calculate the high harmonic generation spectrum for a wide range of static-field strengths. The possibilities for visualizing low-frequency (terahertz and mid-infrared) radiation using time-delay measurements of even high harmonics intensities are discussed.

Ionized Molecular Hydrogen Build-Up and Confinement Inside the Space Charge of a Continually Resupplied Electron Cloud

A cylindrically symmetric electromagnetic ion trap has been constructed that creates a potential well suitable for confining ions with the space charge of a continually resupplied electron cloud. The trap uses permanent magnets to form a linear array of magnetic field ring cusps in a cylindrical geometry and includes electrostatic plugging of the cusping magnetic fields. The ion source is electron bombardment ionization of a controlled leak of thermal molecular hydrogen directly inside the trap, and a potential well created by those selfsame electrons is the mechanism of ion confinement. The ion trap is unique in that the confinement volume has relatively minimal external static electric and magnetic field intrusion into the regions intended to confine ions and no overall axial magnetic field. Another standout feature is the inclusion of electrostatic elements in two locations inaccessible to electrons inside the trap that provide axial ion confinement in conjunction with electrons in the trap. Build-up of ions, and therefore confinement, was demonstrated via an ion signal that increased in intensity over a period of several dozen expected axial ion transit times while injecting electrons. A study has been conducted for a range of incident electron currents from the electron flood gun for several fixed partial pressures of molecular hydrogen and interpreted using a full particle-in-cell simulation of the trap. Data were acquired via a microchannel plate and phosphor screen assembly biased in a manner that could only be excited by positively charged particles exiting the trap. An order of magnitude estimate for mean lifetime is made using a combination of simulated charged particle population estimates and measured data.

Response of reactive species generation and biological inactivation to electromagnetically assisted cold plasma jets

External static electric and magnetic fields aligned parallel to the propagation direction of a plasma jet affect its dynamic characteristics and the response of reactive species present. A positive electric field was shown to enhance the intensity of ionization waves and the number of positive ions, thereby promoting the generation of aqueous OH and the inactivation of tumor cells subjected to the plasma jet. Correspondingly, the concentration of aqueous O2− and sterilization by the plasma jet gradually increase with increasing negative electric field intensity. The application of an external magnetic field induces a deformation of the plasma plume, manifesting specifically as a radial contraction/expansion of the plasma plume inside/outside the quartz tube because of the influence of magnetic pressure. In addition, with the external magnetic field, the generation of reactive species and the biological inactivation within the plasma jet are improved and can be attributed to the enhanced discharge arising mainly from electrons confined by the axial magnetic field and the radial magnetic pressure. Our work shows that external magnetic fields are well suited to improving the energy efficiency with regard to plasma jet applications, whereas external electric fields provide a means to manipulate the flux and composition of reactive species over the substrate downstream.

Relationships between spherical and bispherical harmonics, and an electrostatic T-matrix for dimers

Bispherical harmonics are the solutions to Laplace’s equation in bispherical coordinates. We investigate the relationships between spherical harmonics and bispherical harmonics in terms of radial inversion and derive new series expansions between the harmonics. The series coefficients are the Delannoy numbers encountered in combinatorics, and we exploit the series to derive for them a new second order homogeneous recurrence relation. We use the T-matrix/null field method to solve for the potential of two different spheres in an arbitrary static external electric field, as a series of bispherical harmonics where the coefficients are related via matrix transformations. The matrix elements are expressed as surface integrals of bispherical harmonics, for which analytic expressions are derived in terms of Legendre functions. The resonant values of the dielectric function are computed via an eigenvalue problem which is found to be more stable than the solution using difference equations. The rate of convergence of the matrix formulation is compared to the re-expansion method using spherical harmonics for a uniform field an a dipole in the gap; each series converges faster in a different region of space, which we discuss in terms of the boundaries of convergence of each solution and the image singularities of the scattered field.

External electric field enhances CO2 geological Storage: A molecular dynamics simulation

The microscopic understanding of adsorption and storage of CO2 in minerals is of great significance for large-scale geological storage of CO2. The behaviors of the H2O − CO2 system absorbed on the kaolinite surfaces with oscillating and static electric fields were investigated by the non-equilibrium molecular dynamics simulation. The results show that the H2O molecules will adsorb onto clay surfaces and reduce the adsorption of CO2, which results in lower amounts of geological storage of CO2. However, the applied external static electric fields can break hydrogen bonds which formed between H2O molecules and clay surface, and thus promote the desorption of H2O and geological storage of CO2. The static electric fields are more pronounced in enhancing CO2 geological storage with an extra 15.58 % when the surface is vertical to the electric field direction. Meanwhile, the initial dipole orientation of H2O in the adsorption phase, which is parallel to the surface, decides that electric fields are more efficient on the surface vertical to the electric field direction. This research will be helpful to understand how electric fields promote CO2 geological storage on the molecular level.

Frequency-Tunable Slot-Loop Antenna Based on KNN Ferroelectric Interdigitated Varactors

A miniature frequency-tunable slot-loop antenna (0.128 λ 0 × 0.077 λ 0) based on ferroelectric K0.5Na0.5NbO3 (KNN) interdigitated varactors is investigated at Ku-band. KNN material has been selected among the ferroelectric oxide family because of its competitive properties for microwave applications. Its high permittivity value ( ϵr a 360 at 10 GHz) and its wide frequency tunability under an external static electric field E bias make it a promising candidate for frequency-agile antennas and circuits at microwaves. The antenna prototype has been designed and elaborated on MgO substrate ( ϵr = 9.8 and tan δ a 10−4 at 10 GHz). Fabrication details including laser microetching process of the ferroelectric layer are also described. The center frequency of the slot-loop antenna can therefore be tuned monotonously from 15.22 to 15.97 GHz under E bias = 88 kV/cm, leading to a frequency tunability rate equal to 4.6%. These results demonstrate for the first time the ability of the KNN material to be used for miniature tunable antennas, in comparison with BaxSr1−xTiO3, currently considered as the most relevant material for such applications.

Non-equilibrium molecular dynamics study of human aquaporin-2 in the static external electric fields

In this paper, non-equilibrium MD simulations (NEMD) of human aquaporin-2 (AQP2) in the presence of an external static electric field have been performed along + z and − z directions of the pore axis. The impacts of the electric field direction on the gating mechanism corresponding to the selectivity filter (SF) region of AQP2 have been studied. Besides, the effects of applied external electric field on the PMF profile of water molecules translocation, water permeability, and molecules dipole orientation are investigated. Our results showed that when the external electric field is implemented along the + z direction of the channels, the selectivity filter region is kept in the wide conformation for the majority of the time. Therefore, a remarkable increase in the overall water permeability can be seen compared to the case without any external electric field. This is in contrast to the effects of − z-directed electric field on the conformations of the selectivity filter, which induces mostly narrow conformations in this constriction region. A substantial higher energy barrier emerged in the middle of the AQP2’s pores under the effect of –z-directed electric field in comparison with the zero and + z-directed electric field strengths, which is mainly ascribed to the deviation from bipolar dipole orientation within the AQP2’s pores. Communicated by Ramaswamy H. Sarma