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The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics
Journal Prestige (SJR): 0.387  Citation Impact (citeScore): 1 Number of Followers: 29  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1434-6060 - ISSN (Online) 1434-6079 Published by Springer-Verlag  [2469 journals]
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- Modification of PMMA surface hydrophobic properties using an
atmospheric-pressure plasma jet array for the enhancement of flashover
voltage-
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Abstract: The surface insulation performance of insulating materials is crucial for the electrical equipment safe operation and power system stable operation. The improvement of the surface hydrophobicity of insulating materials is important to improve surface flashover voltage. In this paper, an Ar/hexamethyl disiloxane (HMDSO) atmospheric-pressure plasma jet array is constructed to improve the surface hydrophobicity and insulation performance of polymethyl methacrylate (PMMA). With the discharge characteristics and water contact angle (WCA) measurements at different HMDSO contents and treatment times, the surface hydrophobicity of PMMA can be improved significantly and the maximum WCA value can reach about 153°, which meets the standard of super-hydrophobic surface and be benefit of free pollution and moisture. The physical and chemical changes in the treated PMMA surface at the optimal treatment conditions (60 s treatment time and 0.08% HMDSO content) and the untreated PMMA surface are investigated by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It is found that the treated PMMA surface is covered with the dense nanoscale film and silicon containing hydrophobic groups. The corona onset, dry and wet flashover voltages of the PMMA surface before and after jet array treatment are compared. It is found that the corona onset voltage is increased from 10.0 to 13.8 kV, the dry flashover voltage is increased from 15.1 to 19.2 kV, and the wet flashover voltage is increased from 8.2 to 12.4 kV. The mechanisms of the enhancement of the surface insulation performance of insulating materials and the surface hydrophobic modification are discussed. Graphic abstract
PubDate: 2022-05-21
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- Visualizing multiqubit correlations using the Wigner function
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Abstract: Quantum engineering now allows to design and construct multi-qubit states in a range of physical systems. These states are typically quite complex in nature, with disparate, but relevant properties that include both single and multi-qubit coherences and even entanglement. All these properties can be assessed by reconstructing the density matrix of those states—but the large parameter space can mean physical insight of the nature of those states and their coherence can be hard to achieve. Here, we explore how the Wigner function of a multipartite system and its visualization provides rich information on the nature of the state, not only at illustrative level but also at the quantitative level. We test our tools in a photonic architecture making use of the multiple degrees of freedom of two photons. Graphic abstract)
PubDate: 2022-05-20
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- Silicon dumbbell-shaped micro-ring resonator for glucose monitoring
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Abstract: The use of a newly designed silicon dumbbell-shaped micro-ring resonator-based device was conceptualised for sensing applications. In particular, an illustrative example of glucose monitoring was presented considering various values of its concentrations in deionized water. The device operates on the principle of field coupling in integrated optic circuits. To be more specific, the configuration incorporates a specially designed silicon micro-ring resonator placed in the proximity of a straight optical waveguide, which serves as the input and output ports for the optical power. The values of quality factor and time delay were determined in the absence/presence of measurands of different concentrations. The results reveal the specially configured optical waveguide design to be highly sensitive for glucose monitoring applications. Graphical abstract The use of newly designed silicon dumbbell-shaped micro-ring resonator-based device was conceptualised for sensing applications. In particular, an illustrative example of glucose monitoring was presented considering various values of its concentrations in deionized water. The device operated on the principle of field coupling in integrated optic circuits. To be more specific, the configuration incorporates a specially designed silicon micro-ring resonator placed in the proximity of straight optical waveguide, which serves as the input and output ports for the optical power. The values of quality factor and time delay were determined in the absence/presence of measurands of different concentrations. The results reveal specially configured optical waveguide design to be highly sensitive for such monitoring applications.
PubDate: 2022-05-20
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- Electron-impact excitation of the 5 $$\varvec{\,^2\mathbf{S}_{1/2}
\rightarrow 5\,^2\mathbf{P}_{1/2}}$$ 2 S 1 / 2 → 5 2 P 1 / 2 and 5
$$\varvec{\,^2\mathbf{P}_{3/2}}$$ 2 P 3 / 2 transitions in rubidium by
40 eV electrons: theory and experiment-
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Abstract: We report on a series of detailed Breit-Pauli and Dirac B-spline R-matrix (DBSR) differential cross section (DCS) calculations for excitation of the \(5\,^2\mathrm{S}_{1/2} \rightarrow 5\,^2\mathrm{P}_{1/2}\) and \(5\,^2\mathrm{S}_{1/2}\rightarrow 5\,^2\mathrm{P}_{3/2}\) states in rubidium by 40 eV incident electrons. The early BP computations shown here were carried out with both 5 states and 12 states, while the DBSR models coupled 150 and 325 states, respectively. We also report corresponding results from a limited set of DCS measurements on the unresolved \(5\,^2\mathrm{P}_{1/2,3/2}\) states, with the experimental data being restricted to the scattered electron angular range 2– \(10^\circ \) . Typically, good agreement is found between our calculated and measured DCS for excitation of the unresolved \(5\,^2\mathrm{P}_{1/2,3/2}\) states, with best accord being found between the DBSR predictions and the measured data. The present theoretical and experimental results are also compared with predictions from earlier 40 eV calculations using the nonrelativistic Distorted-Wave Born Approximation and a Relativistic Distorted-Wave model. Graphic abstract
PubDate: 2022-05-20
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- Estimation of distance-distribution probabilities from pulsed electron
paramagnetic resonance (EPR) data of two dipolar interaction coupled
nitroxide spin labels using doubly rotating frames and least-squares
fitting-
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Abstract: A method, based on the doubly rotating frame (DRF) technique to calculate the basis DEER (Double Electron–Electron Resonance) signals [Physica B: Condensed Matter, 625, 413,511 (2022)] accurately by numerical techniques over a range of \(r\) values, where \(r\) is the distance between the two nitroxides in a biradical in a biological system, has been exploited to calculate the probabilities of distance distribution, \(P\left( r \right), \) by the use of Tikhonov regularization. It is demonstrated here by applying it to the data reported by Lovett et al. [J. Magn. Reson., 223, 98–106 (2012)] on a sample of bis-nitroxide nanowire, P1, in deuterated ortho-terphenyl solvent with 5% BnPy (d14-oTP/BnPy) in semi-rigid state. An improvement in the agreement of the calculated signal with respect to the experimental signal and thus in the probabilities of the distance distribution, \(P\left( r \right)\) , so obtained, is found, as compared to that obtained using the kernel signals based on analytical expressions. Graphical abstract
PubDate: 2022-05-19
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- Potassium upconversion violet light generation under two-color two-photon
excitation to 4D, 6S level-
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Abstract: Two-color nanosecond dye lasers were used to excite potassium vapor cell, and 404-nm violet beam output was observed. This violet beam owns good collimation and transient properties, and its wavelength matches with the transition from potassium 52P3/2,1/2 doublet to the ground state. An analysis process shows that the violet light mechanism is attributed to two-photon-induced 42S1/2 → 42P3/2 → 42D3/2,5/2/62S1/2 transition, 42D3/2,5/2/62S1/2 → 52P3/2,1/2 SHRS (stimulated hyper-Raman scattering), and FWM (four-wave-mixing) processes; this is a third-order nonlinear optics process. Violet light doublet-line intensity ratio was found to change while fine scanning of excitation wavelength; this shifting was thought related to the FWM resonant degree. Potassium violet light is expected to become new tunable light source. Graphical abstract
PubDate: 2022-05-17
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- Laboratory experiments on the radiation astrochemistry of water ice phases
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Abstract: Water (H2O) ice is a ubiquitous component of the universe, having been detected in a variety of interstellar and Solar System environments where radiation plays an important role in its physico-chemical transformations. Although the radiation chemistry of H2O astrophysical ice analogues has been well studied, direct and systematic comparisons of different solid phases are scarce and are typically limited to just two phases. In this article, we describe the results of an in-depth study of the 2 keV electron irradiation of amorphous solid water (ASW), restrained amorphous ice (RAI) and the cubic (Ic) and hexagonal (Ih) crystalline phases at 20 K so as to further uncover any potential dependence of the radiation physics and chemistry on the solid phase of the ice. Mid-infrared spectroscopic analysis of the four investigated H2O ice phases revealed that electron irradiation of the RAI, Ic, and Ih phases resulted in their amorphization (with the latter undergoing the process more slowly) while ASW underwent compaction. The abundance of hydrogen peroxide (H2O2) produced as a result of the irradiation was also found to vary between phases, with yields being highest in irradiated ASW. This observation is the cumulative result of several factors including the increased porosity and quantity of lattice defects in ASW, as well as its less extensive hydrogen-bonding network. Our results have astrophysical implications, particularly with regards to H2O-rich icy interstellar and Solar System bodies exposed to both radiation fields and temperature gradients. Graphical abstract
PubDate: 2022-05-17
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- Spectral and dissociation characteristics of aluminum chloride in external
electric field-
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Abstract: Aluminum chloride has great toxicity and threatens the ozone layer. The ground-state geometric structure and spectral characteristics are calculated for various external electric fields via DFT at the B3LYP/6–31 + G(d) basis set level. Aluminum chloride dissociation is directly given by calculating the molecular potential energy curve and potential energy surface. With the external electric field, the structure of aluminum chloride changes significantly. With increase in electric fields, the 1Al-3Cl and 1Al-4Cl bond lengths increase, and the total energy and energy gap initially increase and then decrease, whereas the dipole moment first decreases and then increases. Most vibrational frequencies of infrared and Raman spectra are redshifted. When the electric fields intensity is 0.040 a.u., the 1Al-4Cl bond fracture, which means a dissociation of the molecule. When the electric field intensity is 0.045 a.u., the aluminum chloride appeared on another dissociation pathway, which may be concerted. These results are of great significance concerning the dissociation mechanism of aluminum chloride in external electric field. Graphical abstract
PubDate: 2022-05-17
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- Gauge dependence of spontaneous radiation spectrum in a time-dependent
relativistic non-perturbative Coulomb field-
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Abstract: Lamb triggered a continuous debate on the gauge choice for atomic interactions with electromagnetic fields, particularly with plane waves and the vacuum field. Modern technologies of Rydberg atoms and relativistic atomic beams make it possible to explore interactions with a more intriguing non-perturbative, adiabatic Coulomb field. In such cases, one would face the well-known tricky issue about the physical significance of the scalar gauge potential when it is time-dependent. We start attacking this issue by studying a simplest system: a one-dimensional oscillator interacting adiabatically with a relativistic charge. We reveal that a gauge dependence much severer than the one Lamb observed is encountered when calculating the transient radiation spectrum of this oscillator by the external-field method, which is currently the only available tool. The obtained peak frequency can differ by 10 MHz or larger for the commonly used Coulomb, Lorentz, and Multipolar gauges. Contrary to the popular view, we explain that such a gauge dependence is not really a disaster, but actually an advantage here: The relativistic bound-state problem is so complicated that a full quantum-field method is still lacking; thus, the external-field approximation cannot be derived and hence not guaranteed. However, by fitting to experimental data, one may always define an effective external field, which may likely be parameterized with the gauge potential in a particular gauge. This effective external field would not only be of phenomenological use, but also shed light on the physical significance of the gauge potential. We thereby encourage further investigations of this fundamental problem with more realistic systems involving Rydberg atoms and relativistic atomic beams, both theoretically and experimentally. Graphic
PubDate: 2022-05-16
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- The scattering symmetries of tetrahedral quantum structures
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Abstract: The electrons associated with molecules and other small quantum structures exist in states that are bound or quasibound to the molecule. The quasibound states, which can significantly affect chemical reaction dynamics, have finite lifetimes and are associated with complex energy poles of the scattering matrix. Using Wigner–Eisenbud (R-matrix) scattering theory, we examine the symmetry properties of the quasibound states of a molecule-size tetrahedral system, and we examine the relation of quasibound states to the scattering properties. In addition, using R-matrix theory, we construct a non-Hermitian Hamiltonian whose complex energy eigenvalues coincide with the bound and quasi-bound states of the molecule. We show that each bound state and quasibound state of the tetrahedral system belongs to a distinct irreducible representation of the tetrahedral group, and that an incident electron belonging to one irreducible representation can only scatter within the same irreducible representation. Graphic
PubDate: 2022-05-16
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- Optimization of high-order harmonic generation for the time-resolved ARPES
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Abstract: We experimentally investigated the optimized phase matching condition for high order harmonic generation as a source of time-resolved Angle-resolved photoemission spectroscopy (TR-ARPES) applications. In the loose focusing scheme, we find that the divergence of harmonics decreases with the increase of gas cell length, while the maximum intensity is obtained with 10–15 mm gas cell. Our result shows that stable beam condition with best temporal resolution can be realized for TR-ARPES by using a longer gas cell (longer than 25 mm in our experiment), and an appropriate gas cell length can provide balanced condition for good beam intensity and good temporal resolution. Graphical abstract
For the experiments carried out on HHG-based TR ARPES, the wavefront tilt of harmonic beam is inevitably introduced by the grating used in monochromator, leading to the boarding of pulse width and the dramatic decrease of the temporal resolution. A simple way to decrease the wavefront tilt is by optimizing the beam quality of high order harmonics. In our work, we aim to decrease the divergence of harmonic beam while keeping the enough intensity. We have experimentally investigated the intensity and beam divergence of high order harmonics generated in Ar for different gas cell condition. The divergence of harmonics decreases with the increase of gas cell length which is shown in (a), while the maximum intensity is obtained with 10 15 mm gas cell shown in (b). Our result c d shows that stable beam condition with best temporal resolution can be realized for TR ARPES by using a longer gas cell, and an appropriate gas cell length can provide balanced condition for good beam intensity and good temporal resolution.
PubDate: 2022-05-16
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- Goos–Hänchen shift observed from stratified medium
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Abstract: In this paper, we have theoretically examined Goos–Hänchen shift (GHS) obtained from a stratified epsilon-near-zero (ENZ) medium placed in air. Transfer matrix method is used to calculate GHS for a sandwich structure composed of odd number of slabs. The impact of changing the material permittivity, thickness and number of slabs on GHS is discussed in detail for TE and TM polarized light. Significant increase in GHS is observed as the number of ENZ slabs in stratified structure is increased. When all the slabs have equal permittivity, published results for a single ENZ slab are recovered. The presented work will help in designing stratified ENZ medium with required GHS and reflectivity for optical sensors. Graphic abstract
PubDate: 2022-05-12
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- A prospective study on ionization of endohedral metallofullerene as
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Abstract: Since the discovery of endohedral metallofullerene, it has always been attractive among researchers in various fields of utilities. An encapsulated Au atom with fullerene can be an ideal active agent for enhancing the response of the ligand docking site of protein for cryo-electron microscopy. In this study, we have used high energy electron scattering to ionize encapsulated Au atom, which is docked in protein’s cavity. It is to identify the capabilities of encapsulated Au atom as a biomarker for cryo-electron microscopy. We have applied a fully relativistic calculation to calculate differential cross section and spin asymmetry with relativistic wave functions at the high impact energy. The obtained results reflect that endohedral metallofullerene can enhance the scattering amplitude of protein, which could be a biosensing tool for cryo-EM, as well as the study of drug docking with any protein molecule. Graphic
PubDate: 2022-05-11
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- Dynamic behaviour of beta decay constant in H-like atoms with intense
laser-
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Abstract: Beta decay in hydrogen-like atoms is studied under the influence of a linearly polarized laser field. The oscillating electronic cloud under an intense laser field produces a time-varying field around the nucleus. The interaction of this electric field with the nucleus of the hydrogenic system is studied in terms of interaction between the electronic and nuclear charge densities. The nuclear transition matrix for beta decay is calculated by considering the interaction Hamiltonian, and the variations in the decay constant are analyzed. Graphic
PubDate: 2022-05-06
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- The role of dynamic absorption and polarization potentials in relativistic
excitation of xenon-
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Abstract: Data on excitation of rare gases is mainly important in the study of lighting, plasma displays and lasers. From literature, cross sections data on electron impact excitation of low-lying resonance states of xenon atoms with both relativistic and non-relativistic computations often differ with available experimental data mostly at low and intermediate impact energies and at intermediate scattering angles. With this in view, we have applied relativistic effects in a fully relativistic distorted-wave born approximation approach to excitation of the lowest lying resonance states of a xenon target atom in a complex potential in order to solve the Dirac equations to obtain the free electron wavefunctions and corresponding excitation cross sections. Present differential cross sections (DCS) results from this study predict that absorption effects in the distortion potential generally have minimal effect on cross sections at impact energies below 50 eV, but then significantly improve these results in comparison with experiments as kinetic energy of the incident electron increases. Furthermore, it is evident that the energy dependent dynamic polarization potential adopted plays a major role in improving shapes of cross sections at low and near threshold impact energies, where other distorted-wave methods fail to give satisfactory results. Graphical abstract We have applied a fully relativistic distorted-wave (RDW) approach to inelastic excitation of the lowest J = 1 states of xenon in which a complex potential (SEPA = static (S), + exchange (SE), + polarization (SEP) and + absorption (SEPA)) is used to solve the Dirac equations to obtain electron initial and final wave functions \(\chi_{a}^{ + }\) and \(\chi_{b}^{ + }\) respectively). The transition matrix \(T_{a \to b}^{RDW} = \left\langle {\chi_{b}^{ - } \left {V - U} \right A\chi_{a}^{ + } } \right\rangle\) is then used to obtain the differential cross sections. Theoretical studies on excitation of xenon J = 1 states [1–3] have not yet applied this approach. Experimental (Expt.) results are in bullets while calculations are in full and dotted lines. Present DCS results predict that the polarization potential plays a major role of improving cross sections at low and near excitation threshold while absorption does this above 50 eV.
PubDate: 2022-05-06
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- Photofragmentation dynamics study of ArBr $$_2$$ 2 $$(v=16,\ldots ,25)$$ (
v = 16 , … , 25 ) using two theoretical methods: trajectory surface
hopping and quasiclassical trajectories-
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Abstract: The vibrational predissociation of van der Waals complexes has been the object of study using a wide range of theoretical and experimental methods, producing a large number of results. We focus here on the ArBr \(_2\) ( \(v=16,\ldots ,25\) ) system. For its study, we employ two important theoretical methods: the trajectory surface hopping (TSH) and the quasiclassical trajectory method (QCTM). In the first case, the dynamics of the system are reproduced on a potential energy surface (PES) corresponding to quantum molecular vibrational states. The possibility of hopping to other vibrational surfaces is also included, which can then lead to van der Waals bond dissociation. On the other hand, the second case consists of propagating the dynamics over a single potential energy surface. We incorporate the kinetic mechanism into the TSH method for better comparison of the evolution of the complex. Both methods allow us to study the dynamical behavior of the ArBr \(_2\) as well as several observables. We compute the lifetime, exit channel, rotational energy, and maximum angular momentum ( \(j_{max}\) ) of Br \(_2\) . We compare our results with previous experimental and theoretical work and also report new results for cases that have not previously been considered. Graphical abstract
PubDate: 2022-05-06
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- Design and development of dielectric barrier discharge setup to form
plasma-activated water and optimization of process parameters-
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Abstract: In the present work, a co-axial cylindrical plasma device has been designed and developed to generate dielectric barrier discharge to form plasma-activated water (PAW). The voltage–discharge current characteristics and optical emission spectroscopy are performed to characterize the plasma and identify the formed plasma species. The impact of process parameters on physicochemical properties of PAW and on the concentration of reactive oxygen–nitrogen species is studied using a design of experiment methodology. The obtained results are analyzed using analysis of variance, effect estimation, marginal means, and regression analysis. The optimum values of process parameters to form PAW are determined using MATLAB fmincon function. The obtained results show that plasma–water exposure time and plasma discharge power significantly influence the physicochemical properties of PAW and the concentration of NO3‾ and NO2‾ ions in plasma-activated water. Graphical abstract
PubDate: 2022-05-05
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- On the temperature of large biomolecules in ion-storage rings
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Abstract: A method to determine the temperature of molecular ions in an ion-storage ring is presented. Molecular ions were repeatedly irradiated by laser pulses over several hundred milliseconds, and the rate of fragmentation was used to determine the temperature of the photoexcited ions. The initial temperature of the ions before photoabsorption was in turn found from the microcanonical caloric curve for the molecule of interest. The temperature evolution of the protonated GFP chromophore in the ELISA storage ring was found for different starting conditions by this method. We find that the initial temperature of the ions when entering the ring depends on the ion-trap temperature and the amount of buffer gas used in the trap. In particular, collisional heating during acceleration after the ion trap can be significant. Protonated GFP chromophores, produced under different conditions, were used to determine temperature effects on the gas-phase absorption spectra. Graphical abstract
PubDate: 2022-05-04
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- Attosecond coupled electron-nuclear dynamics of H $$_2$$ 2 molecule under
intense laser fields-
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Abstract: Sequential double ionization and fragmentation dynamics of the H \(_2\) molecule exposed to an 750 nm, 4.5 fs elliptically polarized laser pulse is investigated by employing a quasi-classical model. In the model, momentum-dependent auxiliary potentials are added to the Hamiltonian to account for non-classical effects. Through theoretical exploitation of the molecular clock technique, the evolution of the vibrational wave packet of H \(_2^+\) formed by over-the-barrier ionization of the H \(_2\) molecule is tracked between the first and second ionization events with the temporal resolution of 140 attoseconds. The role of electron correlation in strong field ionization is captured. Our results show that the quasi-classical model is quite capable of describing and predicting light-induced multi-electron processes in the molecules. Our study provides a simple path of explaining and understanding the physical mechanism of the strong field multi-electron processes. Graphic abstract
PubDate: 2022-05-03
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- Publisher Correction to: Theoretical calculations of the photoionization
cross sections for the ground and lowest two excited states of Ni XVIII
ion-
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PubDate: 2022-05-02
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