Static Dipole Research Articles

Elastic electron scattering by halocarbon radicals in the independent atom model approach

In order to study the elastic scattering of electrons by CFn (n = 1 − 4) molecular targets the independent atom model (IAM) is used with the optical potential (OP) method. The scattering cross sections were calculated in two approximations of the model – the IAM approach is used for the differential, while the Additivity Rule (IAM-AR) is used for the integral cross sections. The amplitudes of electron scattering by the carbon and fluorine atoms of the target molecules are calculated from the corresponding phase shifts, using the real and complex optical potential method. The parameter-free real part of the OP is calculated from the corresponding atomic characteristics – nuclear charge, electron density and static dipole polarizability. The differential and integral cross sections are calculated at equilibrium internuclear distances of the CFn molecules. They were compared with the available experimental data and with other theoretical results. A good overall agreement was observed while comparing our integral cross sections with the measured data. The level of the agreement however strongly depends on the target molecule, and a good consistency is observed typically above certain collision energies: from 10 eV in case of CF2, above 15-20 eV for CF3 and from 40 eV in case of CF4. Similar tendencies were found in case of the differential cross sections for a wide range of scattering angles at collision energies above 10 eV in case of CF2, above 15–20 eV for CF3, while in case of CF4 – above 20 eV.Graphical abstract

High pressure effects on the excitation spectra and dipole properties of Li, Be+, and B2+ atoms under confinement

Properties of atoms and molecules undergo significant changes when subjected to spatial confinement. We study the excitation spectra of lithium-like atoms in the initial 1s22s electronic configuration when confined by an impenetrable spherical cavity. We implement Slater’s X-α method in Hartree–Fock theory to obtain the excitation spectrum. We verify that as the cavity size decreases, the total, 2s, 2p, and higher excited energy levels increase. Furthermore, we confirm the existence of crossing points between ns–np states for low values of the confinement radius such that the ns → np dipole transition becomes zero at that critical pressure. The crossing points of the s–p states imply that instead of photon absorption, one observes photon emission for cavities with radius smaller than the critical radius. Hence, the dipole oscillator strength associated with the 2s → 2p transition becomes negative, and for higher pressures, the 2s → 3p dipole oscillator strength transition becomes larger than unity. We validate the completeness of the spectrum by calculating the Thomas–Reiche–Kuhn sum rule, as well as the static dipole polarizability and mean excitation energy of lithium-like atoms. We find that the static dipole polarizability decreases and exhibits a sudden change at the critical pressure for the absorption-to-emission transition. The mean excitation energy increases as the pressure rises. However, as a consequence of the critical transition from absorption to emission, the mean excitation energy becomes undetermined for higher pressures, with implications for material damage under extreme conditions. For unconfined systems, our results show good to excellent agreement with data found in the literature.

Relevance of the Quadratic Diamagnetic and Self-Polarization Terms in Cavity Quantum Electrodynamics.

Experiments at the interface of quantum optics and chemistry have revealed that strong coupling between light and matter can substantially modify the chemical and physical properties of molecules and solids. While the theoretical description of such situations is usually based on nonrelativistic quantum electrodynamics, which contains quadratic light–matter coupling terms, it is commonplace to disregard these terms and restrict the treatment to purely bilinear couplings. In this work, we clarify the physical origin and the substantial impact of the most common quadratic terms, the diamagnetic and self-polarization terms, and highlight why neglecting them can lead to rather unphysical results. Specifically, we demonstrate their relevance by showing that neglecting these terms leads to the loss of gauge invariance, basis set dependence, disintegration (loss of bound states) of any system in the basis set limit, unphysical radiation of the ground state, and an artificial dependence on the static dipole. Besides providing important guidance for modeling of strongly coupled light–matter systems, the presented results also indicate conditions under which those effects might become accessible.

Theoretical and Experimental Salvation of Nano Copper Sulfate Interacted with 18-crown-6 in Water

Theoretical study of the electronic structure, NonLinear Optical (NLO) properties, and natural bonding orbital (NBO) analysis of 18-crown-6were investigated using Density Functional Theory DFT) calculations at the B3LYP/6-311G (d,p) level of theory. The optimized structure is a nonlinear compound indicated from the dihedral angles. Natural bonding orbital analysis has been analyzed in terms of the hybridization of each atom, natural charges (Core, Valence, and Rydberg), bonding and antibonding orbital's second-order perturbation energy (E(2)). The calculated EHOMO and ELUMO energies of the title molecule can be used to explain the charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), softness(S), global electrophilicity index (w), and electronegativity (χ). The NLO parameters: static dipole moment (µ), polarizability (α), anisotropy polarizability (Δα), first-order hyperpolarizability (βtot) and third-order hyperpolarizability ⟨γ⟩), of the studied molecule have been calculated at the same level of theory.The Molecular Electrostatic Potential (MEP) and ElectroStatic Potential (ESP) for the title molecule were investigated and analyzed. Also, the electronic absorption spectra were discussed by time-dependent density functional theory (TD-DFT) calculations in ethanol and water solvents. From the experimental conductance measurements, the association thermodynamic parameters (KA, ∆GA, ∆HA, and ∆SA) and complex formation thermodynamic parameters (Kf, ∆Gf, ∆Hf, and ∆Sf) of nano-CuSO4 in presence of 18-crown-6 as a ligand in 10% ethanol-waterer solvents at different temperatures (298.15, 303.15, 308.15 and 313.15K) were applied and calculated.

Comparative analysis of nonrelativistic and relativistic calculations of electric dipole moments and polarizabilities of heteronuclear alkali-metal dimers

We analyze the molecular electric dipole moments (PDMs) and static electric dipole polarizabilities of heteronuclear alkali dimers in their ground states by employing coupled-cluster theory, both in the non-relativistic and four-component relativistic frameworks. The roles of electron correlations as well as relativistic effects are demonstrated by studying them at different levels of theory, followed by a comprehensive treatment of error estimates. We compare our obtained values with the previous non-relativistic calculations, some of which include lower-order relativistic corrections, as well as with the experimental values, wherever available. We find that the PDMs are very sensitive to relativistic effects, as compared to polarizabilities; this aspect can explain the long-standing question on the difference between experimental values and theoretical results for LiNa. We show that consideration of relativistic values of PDMs improves significantly the isotropic Van der Waals $C_6$ coefficients of the investigated alkali dimers over the previously reported non-relativistic calculations. The dependence of dipole polarizabilities on molecular volume is also illustrated.

Molecular quantum materials: electronic phases and charge dynamics in two-dimensional organic solids

This review provides a perspective on recent developments and their implications for our understanding of novel quantum phenomena in the physics of two-dimensional organic solids. We concentrate on the phase transitions and collective response in the charge sector, the importance of coupling of electronic and lattice degrees of freedom and stress an intriguing role of disorder. After a brief introduction to low-dimensional organic solids and their crystallographic structures, we focus on the dimensionality and interactions and emergent quantum phenomena. Important topics of current research in organic matter with sizeable electronic correlations are Mott metal-insulator phase transitions, charge order and ferroelectricity. Highly frustrated two-dimensional systems are established model compounds for studying the quantum spin liquid state and the competition with magnetic long-range order. There are also unique examples of quantum disordered state of magnetic and electric dipoles. Representative experimental results are complemented by current theoretical approaches.

Polarizabilities and tune-out wavelengths of the hyperfine ground states of 133Cs atom

SynopsisThe static and dynamic electric dipole polarizabilities of the ground state and hyperfine ground states of the 133Cs have been calculated by using relativistic configuration interaction plus core polarization (RCICP) approach. The tune-out wavelengths of ground and hyperfine ground states are also determined.

Relativistic configuration interaction with core polarization method for the divalent systems

SynopsisThe relativistic configuration interaction with core polarization method and program for the divalent systems have been developed. Based on this new program, the energy levels, transition matrix elements, static and dynamic dipole polarizabilities of He, Be, and Mg atoms have been calculated systematically.

Long-range potentials and dipole moments of the CO electronic states converging to the ground dissociation limit.

The asymptotic, R → ∞, behavior of the potential-energy and dipole-moment functions (PEFs and DMFs) for all six (1,2)Σ+, (1,2)Π, Σ-, and Δ electronic states converging to the ground C(3P) + O(3P) dissociation limit of the CO molecule are studied in the framework of long-range (LR) perturbation theory. The analytical expressions for the leading coefficients of the LR expansion, C5/R5 for PEF and d4/R4 for DMF, in terms of the atomic quadrupole constants and static dipole polarizabilities are derived. The exact relationships between the LR coefficients for the states of different spatial symmetry are established as well. The analytical results are complemented with the first-principles calculation of the PEFs and DMFs for all the above states at large distances (R = 5-20 Å). The electronic structure calculation is conducted by means of the multi-reference configuration interaction and the averaged-coupled-pair functional methods, which both implemented the aug-cc-pwCVXZ (X = T, Q, and 5) basis sets and finite-field approach. The dispersion coefficients, C5 and C6, extracted from the ab initio PEFs, are found to be very close to their present and previous theoretical counterparts. The analytically estimated d4 = -5 DÅ4 obtained for the ground X1Σ+ state perfectly agrees with the present ab initio DMF but diverges significantly from the literature data.

Measurement of the \(\gamma \) Decay from the Energy Region of the Pygmy Dipole States Excited in the \(^{208}\)Pb\((p,p'\gamma )\) Reaction at CCB

For a few years, the medical cyclotron Proteus C-235 at the Cyclotron Centre Bronowice in Krakow, Poland has been regularly used for nuclear structure experiments. One of the ongoing studies is focused on the γ decay of collective states populated in (p, p0γ) reactions. In a recent experiment, γ decays of excited states in the energy region of the Pygmy Dipole States in 208Pb have been observed. Good efficiency and energy resolution provided by the PARIS clusters and LaBr3:Ce scintillators facilitate a comparison of the obtained energy spectra with previous measurements of pygmy states in this nucleus.

Oscillating nuclear electric dipole moment induced by axion dark matter produces atomic and molecular electric dipole moments and nuclear spin rotation

According to the Schiff theorem, a static nuclear electric dipole moment (EDM) does not produce atomic and molecular EDMs. However, interaction with the axion dark matter field generates nuclear EDMs ${\mathbf{d}}_{N}={\mathbf{d}}_{N}^{0}\mathrm{cos}(\ensuremath{\omega}t)$ which oscillate with the frequency $\ensuremath{\omega}={m}_{a}{c}^{2}/\ensuremath{\hbar}$. These oscillating nuclear EDMs generate atomic and molecular EDMs proportional to ${\ensuremath{\omega}}^{2}$. The resulting atomic and molecular EDMs do not, however, lead to nuclear spin rotation in constant external electric fields. On the other hand, an oscillating electric field penetrates atoms and molecules and can interact with nuclear EDMs. Moreover, if the nuclear EDM oscillation frequency is in resonance with the external field, nuclear spin rotation happens, with the rotation angle growing linearly with time.

Infrared Interlayer Exciton Emission in MoS_{2}/WSe_{2} Heterostructures.

We report light emission around 1eV (1240nm) from heterostructures of MoS_{2} and WSe_{2} transition metal dichalcogenide monolayers. We identify its origin in an interlayer exciton (ILX) by its wide spectral tunability under an out-of-plane electric field. From the static dipole moment of the state, its temperature and twist-angle dependence, and comparison with electronic structure calculations, we assign this ILX to the fundamental interlayer transition between the K valleys in this system. Our findings gain access to the interlayer physics of the intrinsically incommensurate MoS_{2}/WSe_{2} heterostructure, including moiré and valley pseudospin effects, and its integration with silicon photonics and optical fiber communication systems operating at wavelengths longer than 1150nm.

Toroidal dipolar bound state in the continuum and antiferromagnetic in asymmetric metasurface

The toroidal dipole (TD) with weak coupling to the electromagnetic fields promises tremendous capability in sensing, light absorption and optical nonlinearities. Here, we analyze the near-field coupling effects of an asymmetric all-dielectric metasurface with an array of high-index Mie-resonant dielectric tetramer cluster. Two distinct optical toroidal dipolar bound states in the continuum are identified from the asymmetric metasurface. One occurs at the internal gap of the tetramer cluster array (intra-cluster toroidal modes), and the other arises from two neighboring clusters (inter-cluster toroidal modes). Via control of the asymmetry of the cluster, the TD could transform from bound states in the continuum into leaky resonances with high-Q factors. The optical antiferromagnetic response could also be identified from the tetramer cluster arrays. The toroidal and antiferromagnetic effects come from the trapped modes with symmetry breaking. These robust responses of the asymmetric metasurface remain stable as the asymmetry degree increases and the polarization of the incident light changes. The proposed metasurface with efficient light–matter interaction serves as a platform for controlling and exploiting optical toroidal and antiferromagnetic excitations.

Polarizabilities, dispersion coefficients, and retardation functions at the complete basis set CCSD limit: From Be to Ba plus Yb.

Static and dynamic polarizabilities of alkaline earth metal atoms Be-Ba and of the Yb atom, as well as dispersion coefficients and retardation functions for their long-range interactions, are used as a benchmark for the restricted coupled cluster method with singles and doubles (CCSD) and noniterative triples added [CCSD(T)] and related polarization propagator CCSD(3) methods at the complete basis set limit. The latter is attained through the sequence of the augmented correlation-consistent polarized weighted core valence n-zeta basis sets with the exact 2-component approximation for the scalar relativistic effects and with the small-core effective core potentials (for Ca, Sr, and Ba). At the converged level of core correlation treatment, the finite-field CCSD(T) method reproduces the best available data for the static dipole and quadrupole polarizabilities better than 1% and 4%, respectively. Systematic cancelation of the triple contribution in the CCSD(3) calculations of the dynamic polarizabilities of alkaline earth metal atoms makes their dispersion coefficients accurate within 3%. The retardation functions are computed and used for the analysis of the long-range interactions in the homonuclear dimers. Implications to accurate ab initio calculations of the global interaction potentials are discussed.

Low-lying dipole and quadrupole states

We briefly review the main properties of the low-lying dipole states known as Pygmy Dipole Resonance trying to select the main one which could define this new excitation mode. A good candidate seems to be the isoscalar-isovector mixing. This mixing, more effective at the nuclear surface, has been proved by both theoretical and experimental investigations. On the other hand, the study of the low-lying quadrupole states does not seem to provide clear evidence for a new excitation mode. The theoretical approaches used to investigate the quadrupole response reach different conclusions and the experimental data can only clearly establish the multipolarities of the states and their one-phonon character. Moreover, cross section calculations are not sensitive enough to disentangle between quadrupole states which are considered, in one of the theoretical approach, as due to different excitation mode.

Gamma-decay from dipole vibrations: Probe for nuclear properties

A review of selected experimental works on the gamma-decay from the Giant and Pygmy Dipole Resonances is presented. The common feature of these experiments is that gamma-decay originates from dipole states populated using reactions induced by heavy ions. The focus is the investigation of dipole modes built on the ground and excited states. The major developments made during the years regarding the detection of high-energy gamma-rays are briefly discussed together with specific results concerning a chosen number of problems among those that were addressed by the theoretical works of P.F. Bortignon. They are: i) the dipole mode in the initial stages of reactions among heavy ions with different $ N/Z$ values for the target and projectile; ii) the problem of isospin symmetry in nuclei at finite temperature; iii) pygmy states far from stability; iv) the nature of the pygmy states.

Fabrication of Electroluminescence Device for PEDOT:PSS / ploy TPD/Eu2O3 Nanoparticles junction

We manufactured the nanoparticles light emitting diode (NPs-LED) for organic and inorganic semiconductors to achieve electroluminescence (EL). The nanoparticles of Europium oxide(Eu2O3) were incorporated into the thin film layers of the organic compounds, poly(3,4,- ethylene dioxythiophene)/polystyrene sulfonic acid (PEDOT:PSS), N,N’–diphenyl-N,N’ –bis(3-methylphenyl)-1,1’-biphenyl 4,4’- diamine (poly TPD) and polymethyl methacrylate (PMMA), by the spin coating and with the help of the phase segregation method. The EL of NPs-LED, was study for the different bias voltages (20, 25, 30) V at the room temperature, from depending on the CIE 1931 color spaces and it was generated the white light at 20V, the orange light generation at 25Vand the red light at 30 V. That by benefit from transition between deep levels in energy gap for Eu2O3 NPs (surface state) and magnetic dipole states for Eu+ (5D0-3 and5L6 to 7F0-6). The Current – Voltage (I-V) Behavior demonstrate that the current comparative with the voltage was good and the knee voltage was 5 V. The EL spectrum shows a broad band emission, the range from EL 350 - 700 nm. Finally, the range of correlated color temperature (CCT) it was between (1200 to 4000).

Dynamics of Preferential Solvation of 5-Aminoquinoline in Hexane-Alcohol Solvent Mixtures.

Dynamics of preferential solvation of 5-aminoquinoline (5AQ) has been studied in hexane-alcohol solvent mixtures. Significant spectral red shift and fluorescence quenching are observed, even for miniscule amounts of alcohols. A nonlinear variation of these parameters, with alcohol mole fraction, indicates dipolar enrichment around 5AQ in its excited state. A nanosecond rise at the red end of emission spectra is ascribed to translational diffusion of alcohol molecules and consequent preferential solvation of 5AQ. Electrostatic stabilization and hydrogen bonding between the dipolar excited state of the fluorophore and polar alcohol molecules are major driving factors here. Time evolution of emission spectra, from those in a predominantly hexane-like environment to those in a predominantly alcohol-like environment, takes place in nanosecond time scale and depends on the alcohol concentration in the mixture. This in agreement with calculations using an existing model. Hence, 5AQ is found to be a suitable fluorescent probe for the study of dynamics in complex systems.

Significance of Prandtl Number on the Heat Transport and Flow Structure in Rotating Rayleigh–Bénard Convection

Abstract A direct numerical simulation of rotating Rayleigh–Bénard convection (RBC) for different fluids (Pr=0.015,0.7,1,7,20, and 100) in a cylindrical cell of aspect ratio Γ=0.5 is carried out in this work. The effect of rotation on the heat transfer rate, flow structures, their associated dynamics, and influence on the boundary layers are investigated. The Rayleigh number is fixed to Ra=106 and the rotation rates are varied for a wide range, starting from no rotation (Ro→∞) to high rotation rates (Ro≈0.01). For all the Prandtl numbers (Pr=0.015–100), a reduction in heat transfer with increase in rotation is observed. However, for Pr=7 and 20, a marginal increase of the Nusselt number for low rotation rates is obtained, which is attributed to the change in the flow structure from quadrupolar to dipolar state. The change in flow structure is associated with the statistical behavior of the boundary layers. As the flow makes a transition from quadrupolar to dipolar state, a reduction in the thermal boundary layer thickness is observed. At higher rotation rates, the thermal boundary layer thickness shows a power law variation with the rotation rate. The power law exponent is close to unity for moderate Pr, while it reduces for both lower and higher Pr. At extremely high rotation rates, the flow makes a transition to the conduction state. The critical rotation rate (1/Roc) for which transition to the conduction state is observed depends on the Prandtl number according to 1/Roc∝Pr0.5.

Photonic zero-energy modes in a metal-based Lieb lattice

We design a photonic tight-binding system using the dispersive background, and observe the noncompact photonic zero-energy modes for both monopole and dipolar states in a finite Lieb lattice with flat truncations. In such a photonic Lieb system, the compact localization of s, p, and d flat bands is also checked. We show that this photonic zero-energy mode is provided by one dispersive band for singular touching, which has the same frequency with the flat band states. Specially, the zero-energy mode can be completely excited by merely one point source at the flat band frequency, covering all the minority sites and forming a noncompact state. This work may provide a deep understanding about the photonic zero-energy mode for higher order states in the Lieb or other flat band models.