Dipole Moment Of Electron Research Articles

Thermal and Nonthermal Microwave Effects of Ethanol and Hexane-Mixed Solution as Revealed by In Situ Microwave Irradiation Nuclear Magnetic Resonance Spectroscopy and Molecular Dynamics Simulation.

Microwave heating is widely used to accelerate the organic synthesis reaction. However, the role of the nonthermal microwave effect in the chemical reaction has not yet been well characterized. The microwave heating processes of an ethanol-hexane mixed solution were investigated using in situ microwave irradiation nuclear magnetic resonance spectroscopy and molecular dynamics (MD) simulation. The temperature of the solution under microwave irradiation was estimated from the temperature dependence of the 1H chemical shifts (chemical shift calibrated (CSC)-temperature). The CSC-temperature increased to 58 °C for CH2 and CH3 protons, while it increased to 42 °C for OH protons during microwave irradiation. The CSC-temperature of CH2 and CH3 protons reflects the bulk temperature of solution by the thermal microwave effect. The lower CSC-temperature of the OH proton can be attributed to a nonthermal microwave effect. MD simulation revealed that electron dipole moments of OH groups ordered along the oscillated electric field decreased the entropy by absorbing microwave energy and simultaneously increased the entropy by dissipating energy to the solution as the thermal and nonthermal microwave effect. Ordered polar molecules interact to increase hydrogen bonds between OH groups as the nonthermal microwave effect, which explains the lower CSC-temperature of the OH protons. The nonthermal microwave effects contribute to the intrinsic acceleration of the organic reaction.

Magnetic Field Dependence of Excitonic and Optical Properties of InP/ZnS Core/Shell Nanostructure

The effect of a magnetic field on the excitonic and optical properties of an InP/ZnS core/shell nanodot (type I) including the influence of the geometrical confinement effect has been investigated. The exciton binding energy, oscillator strength, linear and nonlinear electronic and optical absorption coefficients, electronic dipole moment, and optical gain are studied for different ratios of the core/shell dot radii with and without the application of a magnetic field. The variational formalism is employed to obtain the electronic properties, whereas a compact density matrix method is applied to determine the optical properties. It is observed that the exciton binding energy is enhanced as the core/shell ratio tends to unity, attempting to reach its well-known two-dimensional (2D) limit. The application of a magnetic field shifts the peak to higher energies. The combined effects of a magnetic field and spatial confinement lead to control over the electronic as well as optical properties. These results will be useful for enhancing the performance of such structures for any desired potential application in optical devices.

Exploring the twisted molecular configurations for tuning their optical and nonlinear optical response properties: A quantum chemical approach

Unlike the previous several investigations on planar donor-π-acceptor chromophores, the present investigation highlights the importance of twisted molecular configurations to effectively tune the optical and nonlinear optical (NLO) response properties. A variety of substitutions are made to design several twisted molecular compounds (1–7). These compounds are designed using pyrenyl and naphthalimide moieties, which are twisted with each other in their molecular configurations. The calculated versus experimental highest intensity absorption energy peaks (3.482 V. 3.444 eV) and experimental ionization potentials (6.07 V. 5.93 eV) of parent compound 1 reproduced reasonably well at M06/6-311G∗∗ methodology. The twisted chromophores show significantly larger amplitudes of third-order NLO polarizabilities (<γ>), which are found to be as large as 778.31 × 10−36 esu for compound 7 at the M06/6-311G∗∗ methodology. The <γ> amplitudes were also compared with planar donor-π-acceptor prototype para-nitroaniline (p-NA) molecule to provide the semi-quantitative assessment. For instance, the <γ> amplitudes of all compounds are about ∼7–∼39 times bigger from the amplitude of p-NA at the same computational level. The origin of larger amplitudes has been traced though three-level model using the TD-DFT results. The larger oscillator strengths, lower transitions energies and larger change between the electronic dipole moment between the ground and the excited states. We believe the present study will not only put these compounds under the spotlight of material science but also provide structure-property relationships in designed compounds.

The effect of functionalization on solubility and plasmonic features of gold nanoparticles

Effect of functionalization on stability, solubility, and plasmonic features of gold nanoparticle with the general formula of Au18(SR)14 in water solvent has been studied in this work. Thiol functional groups including 1,1-mercapto-ethyl alcohol, s-cysteamine, thioglycolic acid, and beta-mercaptoethanol have been used. Electronic band-gap, excitation energies, dipole moment, and hardness for all gold nanoparticles in water solvent were investigated using the quantum mechanical approach. Intermolecular forces, radial distribution function (RDF), mean square displacement (MSD), and solvation free energy were calculated by using simulation methods. Electronic band-gap, and excitation energy analysis show that surface modification of gold nanoparticles can change their electronic and plasmonic properties. The analysis of dipole moments indicates that ligands affect the nanoparticle’s solubility. An increase of hardness and therefore chemical stability can be observed for functionalized nanoparticles compared to the bare structure. Intermolecular energies analyses suggest that structure with 1,1-mercapto ethyl alcohol ligand has the strongest interaction with the solvent. The analysis of RDF diagrams also indicates that the molecule with 1,1-mercapto ethyl alcohol ligand has the sharpest pick. The slope of the linear part of MSD diagrams that is the criterion of solute’s lateral diffusion is the highest value for nanoparticle with 1,1-mercapto ethyl alcohol ligand. Furthermore, functionalization also affects solvation free energy contributions. According to obtained data of quantum mechanical calculations and molecular dynamics simulations, it may be concluded that particle with 1,1-mercapto ethyl alcohol is the best ligand for increasing solubility, stability, and plasmonic functions of Au18(SR)14 structures among the examined ones.

An explanation for the muon and electron g \u2212 2 anomalies and dark matter

We propose simple models with a flavor-dependent global U(1)ℓ and a discrete ℤ2 symmetries to explain the anomalies in the measured anomalous magnetic dipole moments of muon and electron, (g − 2)μ,e, while simultaneously accommodating a dark matter candidate. These new symmetries are introduced not only to avoid the dangerous lepton flavor-violating decays of charged leptons, but also to ensure the stability of the dark matter. Our models can realize the opposite-sign contributions to the muon and electron g − 2 via one-loop diagrams involving new vector-like leptons. Under the vacuum stability and perturbative unitarity bounds as well as the constraints from the dark matter direct searches and related LHC data, we find suitable parameter space to simultaneously explain (g − 2)μ,e and the relic density. In this parameter space, the coupling of the Higgs boson with muons can be enhanced by up to ∼ 38% from its Standard Model value, which can be tested in future collider experiments.

Influence of the donor and conjugation at D–π–A organic sensitizers for dye-sensitized solar cells: a first principle study

In this study, we designed perylene-based organic dye for D–π–A architecture. First, screening the well electron-rich and electron-deficient donor and π-spacer group for efficient dye sensitizer for DSSCs have been simulated using DFT and TD-DFT methods. The theoretical results have shown that the LUMO and HOMO energy levels of the design dyes can ensure a positive effect on the process of electron injection and dye regeneration. The main factors of short-circuit current density influence the light harvesting efficiency and the electron injection rate. On the other hand, electron dipole moment is controlled by the open circuit photovoltage, which improves higher-efficiency photovoltaic devices. The calculated results of the design dye reveal that dye D3 can be used as a potential sensitizer for DSSCs.

On the Second Dipole Moment of Dirac’s Particle

An analysis is presented of the possible existence of the second anomalous dipole moment of Dirac’s particle next to the one associated with the angular momentum. It includes a discussion why, in spite of his own derivation, Dirac has doubted about its relevancy. It is shown why since then it has been overlooked and why it has vanished from leading textbooks. A critical survey is given on the reasons of its reject, including the failure of attempts to measure and the perceived violations of time reversal symmetry and charge–parity symmetry. It is emphasized that the anomalous electric dipole moment of the pointlike electron (AEDM) is fundamentally different from the quantum field type electric dipole moment of an electron (eEDM) as defined in the standard model of particle physics. The analysis has resulted into the identification of a third type Dirac particle, next to the electron type and the Majorana particle. It is shown that, unlike as in the case of the electron type, its second anomalous dipole moment is real valued and is therefore subject to polarization in a scalar potential field. Examples are given that it may have a possible impact in the nuclear domain and in the gravitational domain.

CP violating phase sum rule [formula omitted] for CKM and PMNS matrices

The non-zero Dirac phases δq and δl in the CKM and PMNS mixing matrices signify CP violation. In general they are independent. Experimental data including recent T2K results show, however, that in the original KM parameterization for the mixing matrix, the sum δKMq+δKMl is close to zero with δKMq to be approximately π/2. The KM parameterization may have provided some hints that these phases are actually related and CP is maximally violated. We show that this sum rule can be accommodated in models with spontaneous CP violation where both phases originate from a non-trivial common spontaneous CP violating maximized phase in the Higgs potential. We find some interesting phenomenological consequences for flavor changing neutral current and CP violation for such a model. In particular, data from Bs−B¯s mixing provide very strong constraints on the mass scale for the new neutral scalars in the model, yet the model still allows the electric dipole moments of electron and neutron to reach to their current upper bounds. The model can be tested by near future experiments.

Structural and femtosecond third-order nonlinear optical properties of electron donor – acceptor substituted chalcones: An experimental and computational approach

Structural and third-order nonlinear optical (NLO) properties of two D-π-A-π-A [ (2E)-3-(3-chlorophenyl)-1-(3-nitrophenyl)prop-2-en-1-one (3C3NC) and (2E)-3-(4-fluorophenyl)-1-(4-nitrophenyl)prop-2-en-1-one (FNC)] and one D-π-A-π-D [(2E)-1-(9-anthryl)-3-(4-fluorophenyl) prop-2-en-1-one (FANC)] type chalcone derivatives were investigated experimentally as well as theoretically. All the three chalcones are centrosymmetric (CS) and crystallized in P21/c space group. In crystal packing, all compounds exhibit C–H⋯O hydrogen bonds and π···π interactions. From UV–Vis–NIR absorption spectra, the cut-off wavelength and optical band gaps of the chalcones were evaluated. The thermal stability and the melting point of the chalcones were determined from the TGA/DTA techniques. The ultrafast third-order NLO properties of the three chalcones in solution (0.01 M) were evaluated by Z-scan technique using femtosecond (fs) pulses from Ti: Sapphire laser (∼150 fs, 80 MHz, 800 nm). Third-order nonlinear absorption (NLA) coefficient (β ∼ 10−9 cmW−1), nonlinear refraction (NLR) index (n2∼10−14 cm2W−1), susceptibility (χ(3) ∼ 10−12 esu) and molecular hyperpolarizability (γh ∼ 10−31 esu) were unambiguously determined. The chalcones satisfy the condition to observe reverse saturable absorption (RSA) mechanism (σex > σg). Further, the larger values of σex/σg (∼2–3) indicate that the chalcones would exhibit remarkable optical limiting property. The estimated optical limiting (OL) threshold values are in the order of μJ/cm2. Further, all the chalcones have satisfied the one-photon and two-photon figures of merit conditions (W > 1 and T < 1) for the optical switching applications. In addition to experimental findings, the optimized geometry, HOMO-LUMO energy gap, NLO parameters such as electronic dipole moment, polarizability, first and second hyperpolarizabilities of all the three chalcones were determined theoretically (DFT) for different wavelength at B3LYP/6-311 + G (d,p) basic set. The experimentally determined second-order susceptibilities (Z-scan technique) are reasonably in agreement with the computational values (TD-DFT). The MEP surface revealed that the 3C3NC, FNC and FANC molecules have some potential sites for electrophilic and nucleophilic attack. The experimental and computational NLO data clearly suggest that the nonlinearity of chalcone molecules greatly depends on the electron donor and acceptor strengths of the substituents. Further, all the chalcones are potential materials for optical limiting and optical switching applications.

Parameterized Effective Potential for Excited States and Its Application to the Calculation of Transition Dipole Moments

A parameterized effective potential method that was proposed earlier for the ground state has been developed for excited states with symmetry of the ground state. Various approximations for determining exchange-correlation potentials Vxc, have been discussed. In particular, one of the techniques for constructing a new class of Vxc, which is a functional of the external potential (electron–nucleus interaction) in contrast to traditional approaches, in which Vxc explicitly or implicitly depends on the electron density, have been presented on the basis of the Vxc symmetry requirement. The possibilities of the method have been investigated using the example of calculating the electronic dipole moments of the transition of an НеН molecule with a single-determinant wave function. It has been shown that the proposed method for calculating the transition dipole moments can be considered as a compromise between accuracy and computational effort.

Sensing Performance Investigations on Two-Photon Fluorescent Probes for Detecting β-Amyloid in Alzheimer's Disease.

Alzheimer’s disease (AD) is one of the most common forms of senile disease. In recent years, the incidence of AD has been increasing significantly with the acceleration of the aging process of the global population. However, current clinical drugs can only alleviate the symptoms of AD patients without healing the disease fundamentally. Therefore, it is of great significance to develop an effective small molecule diagnostic reagent for the early diagnosis of AD. In this paper, we employ an integrated approach, including molecular docking simulation and quantum mechanics/molecular mechanics calculation, to investigate the sensing performance of a series of donor–acceptor structural probes for the marker protein of AD (β-amyloid). Results show that the probes display evident fluorescence enhancement when bound to the β-amyloid, suggesting the effect of the environment on the molecular properties. Especially, the two-photon absorption cross-section of the probes increase drastically in the β-amyloid compared to that in vacuum, which results from the larger electron delocalization and dipole moment in the fibrillary-like environment. Thus, one can propose that the studied probes are capable of application in two-photon fluorescent imaging, particularly those containing naphthalene rings as the donor or with a longer spacer group. Our calculations elucidate the experimental measurements reasonably, and further establish possible structure–property relationships that can be used to design novel biocompatible two-photon fluorescent probes for the diagnosis of Alzheimer’s.

Role of electron correlation in the P,T -odd effects of CdH: A relativistic coupled-cluster investigation

We investigate the parity ($\mathcal{P}$) and time-reversal ($\mathcal{T}$) symmetry violating effects in the CdH molecule and perform the relativistic coupled-cluster calculation of the molecular parameters- $E_\text{eff}$, $W_\text{s}$ and $W_\text{M}$ related to the electric dipole moment of electron (eEDM) interaction, the scalar-pseudoscalar (S-PS) nucleus-electron neutral current coupling and the nuclear magnetic quadrupole moment (MQM) interaction with electrons, respectively. We also compute the molecular dipole moment and the magnetic hyperfine structure coupling constant of CdH. The value of $E_\text{eff}$, $W_\text{s}$ and $W_\text{M}$ obtained by us in the said molecule are 12.2 GV/cm, 14.0 kHz and $0.82\times$10$^{33}$ Hz/e cm$^2$, respectively, within an uncertainty of 10\%. Furthermore, we study the trend of electron-correlation in the computed properties of CdH and that of the $\mathcal{P,T}$-odd parameters in the group-12 monohydrides (i.e., ZnH, CdH, and HgH).

Nonadiabatic quantum fluctuations in the neutral ground state of tetrathiafulvalene- p -chloranil

A nonadiabatic resonating Hartree-Fock method is applied to the one-dimensional extended Hubbard model with a staggered site-diagonal potential and Su-Schrieffer-Heeger-type electron-phonon coupling to clarify the lattice and electronic structures in the charge-density-wave (CDW) ground state. It is shown that small spin-Peierls-type domains and large dimerized CDW domains appear in the main CDW state having an equidistant lattice. Interference of breathing and translational motions of these domains constitutes quantum fluctuations. The natures of different domains are analyzed by L\owdin-Feshbach partitioning method. The present results, indicating the domains in the CDW ground state as quantum fluctuations, are consistent with the experimentally observed THz electric-field-induced changes in the electronic dipole moment in the neutral phase of tetrathiafulvalene-$p$-chloranil (TTF-CA).

Influence of CO&lt;sub&gt;2&lt;/sub&gt; Molecules Adsorption on the Electronic Properties of Zigzag and Armchair ZnO Nanotubes

Here, the adsorption behavior of the CO2 molecules on electronic properties of zigzag and armchair ZnO nanotubes (ZnONTs) has been studied at M06-2X/6-31G(d) level of theory. It is found that CO2 molecules can be physically adsorbed on the nanotubes. Two minima structures A (monodentate) and B (bidentate) were found on the potential energy surface. Inspection of the results shows that in zigzag and armchair nanotubes, the monodentate complex is more stable than bidentate complex. Also, the stability of complexes increases by increasing the number of CO2 molecules. Comparison of adsorption energies shows that adsorption of CO2 molecules over zigzag (6, 0) model is stronger than armchair (4,4) model. In this work, the various parameters such as electronic chemical potential (m), hardness (ƞ), softness (S), the maximum amount of electronic charge (DNmax), electrophilicity index (ω), dipole moment and work function were investigated to evaluate the reactivity of structures. It is predicted that the conductivity and reactivity of nanotubes increase upon complexation. Based on the natural bond orbital (NBO) analysis, in all complexes charge transfer occurs from CO2 molecules to the nanotube. Theory of atoms in molecules (AIM) was also applied to characterize OCO2… Zn interaction in nanotubes. In addition, the interaction strength is studied through the reduced density gradient (RDG) function. It is predicted that the ZnONTs can be introduced as a favorable candidate in the design and construction of sensors for detecting CO2 molecules.

Exploring response of Li2 molecule to external electric field: A DFT and SAC-CI study

Quantum chemical calculations are performed using Gaussian16W Software to theoretically investigate the response of Li2 molecule to external electric field. Ground state properties of Li2 molecule in the presence of electric field are modelled using Density Functional Theory(CAM-B3LYP/[6-311++G(3df,3pd)]) while excited states are modelled using Symmetry Adapted Cluster Configuration Interaction theory and 6-311++G∗∗ basis set. The effect of external electric field on ground state properties including structural (bond length, total energy, harmonic vibrational frequency and rotational constant), electronic (dipole moment and polarizability) and thermodynamic (vibrational contribution to partition function, thermal energy, entropy and specific heat capacity) properties is reported. External electric field modifies the charge distribution within the molecule and hence its molecular properties. Potential energy curves and transition dipole moments of 22 states (13Singlet + 9Triplet) are also reported. The computed parameters agree well with the experimental data wherever the later is available.

Cтруктурные и спектральные свойства хинолизидиновых nалкалоидов: квантово-химические расчеты

Structural and spectroscopic properties of quinolizidine alkaloids lupinine and epilupinine stereoisomers were studied theoretically. The influence of the calculation method and structural change in the molecule on the results of geometry and other properties of compounds was considered. The equilibrium geometry, harmonic vibrational frequencies and infrared intensities were obtained by means of density functional theory (DFT/B3LYP) calculations with the splitvalence medium-sized 6-31G(d) basis and Dunning’s correlation consistent basis set cc-pVDZ. From the optimized structure of the (+)-lupinine and (+)-epilupinine molecules, geometric parameters were compared with the literature X-ray experimental data. Structural and vibrational parameters for the (-)-lupinine and (-)-epilupinine molecules are predicted by theoretical calculations at B3LYP/6-31G(d) and B3LYP/cc-pVDZ levels of theory. Some physical characteristics for the title compounds, such as total electronic energy, zero-point energy, rotational constants and dipole moments were also defined by DFT methods. The thermodynamic functions of the title compounds were performed at the same theory levels. Stationary points are identified by the solution of the oscillatory problem.

Electric-field control and noise protection of the flopping-mode spin qubit

We propose and analyze a novel "flopping-mode" mechanism for electric dipole spin resonance based on the delocalization of a single electron across a double quantum dot confinement potential. Delocalization of the charge maximizes the electronic dipole moment compared to the conventional single dot spin resonance configuration. We present a theoretical investigation of the flopping-mode spin qubit properties through the crossover from the double to the single dot configuration by calculating effective spin Rabi frequencies and single-qubit gate fidelities. The flopping-mode regime optimizes the artificial spin-orbit effect generated by an external micromagnet and draws on the existence of an externally controllable sweet spot, where the coupling of the qubit to charge noise is highly suppressed. We further analyze the sweet spot behavior in the presence of a longitudinal magnetic field gradient, which gives rise to a second order sweet spot with reduced sensitivity to charge fluctuations.

Vibrational spectroscopic characterization, electronic absorption, optical nonlinearity computation and terahertz investigation of (2E) 3-(4-ethoxyphenyl)-1-(3-bromophenyl) prop-2-en-1-one for NLO device fabrication

The present study spotlights the key structure-property features of a chalcone derivative (2E) 3-(4-ethoxyphenyl)-1-(3-bromophenyl) prop-2-en-1-one (E3BC) for future applications in nonlinear optical devices through dual approach involving experimental and theoretical techniques. The sample has been characterized by 1H NMR, FT-IR, FT-Raman and terahertz spectroscopies. The experimental results are supported by computational studies using density functional theory. To analyse the 1H NMR spectra, theoretical calculations on chemical shifts were done by GIAO method. Complete vibrational assignments of the vibrational modes have been made on the basis of the potential energy distribution in terms of internal coordinates. The low frequency vibrational modes between 0.2 and 1.8 THz were examined via terahertz time domain spectroscopy. The UV–vis spectrum was recorded in methanol solution. The energies, absorption wavelengths and oscillator strengths of electronic singlet-singlet transitions were determined by time dependent density functional theory. The calculated HOMO-LUMO energy gap is small which reveals that the charge transfer takes place within the molecule and it can be exploited for the nonlinear optical applications. Information about the charge density distribution and the sites of chemical reactivity of the molecule has been obtained by mapping electron density with molecular electrostatic potential. The MEP surface around the bromine atom exhibited the dual nature. Along the C-Br axis the positive electrostatic potential (the σ-hole) is present while the remainder of the surface is negative. Hence bromine atom can interact electrostatically with both nucleophiles and electrophiles. For other atoms no atom-specific effects are found. The stability of the molecule arising from hyper conjugative interactions and charge delocalization has been interpreted using natural bond orbital analysis. The study indicates that the intramolecular charge transfer (n → σ∗, n → π∗ and π → π∗) can induce nonlinearity in the molecule and validates E3BC's candidature to be used as a nonlinear optical active material. In order to understand the nonlinear optical activity of the molecule the calculations of electronic dipole moment, polarizability, anisotropy of polarizability as well as first and second hyperpolarizabilities are performed using finite field approach implemented in the DFT method. The findings suggested that the first order hyperpolarizability of titled molecule is 139 times greater than the value of urea. The high value of first order hyperpolarizability shows that E3BC can be a potential candidate in the nonlinear optical applications. The vibrational contribution to the above properties has also been computed using the self-consistent field wave functions within the double harmonic oscillator approximation.

New halogenated chalcones: Synthesis, crystal structure, spectroscopic and theoretical analyses for third-order nonlinear optical properties

The halogen chalcones have been prepared by a simple condensation reaction of 4-bromoacetophenone with different substituted halogen benzaldehydes by presence of catalyst of sodium hydroxide. The proposed structures were solved and refined by single crystal X-ray diffraction analysis and the optimized molecular structure at the ground state were further performed using density functional theory (DFT) method with B3LYP/6-311G++(d,p) basis set level. The supramolecular C—H⋯O, C—H⋯Cl and C—H···π hydrogen bonds and halogen···halogen interactions observed stabilize and strengthen the crystal structure of the halogen chalcones. All the newly synthesized compounds were characterized by spectroscopic methods including, FT-IR, 1H and 13C NMR and UV-Visible. The experimental geometrical parameters were compared with the calculated TD-DFT, where the values are in good agreement. All compounds exhibiting a good HOMO-LUMO energy gap values in a range of 4.0 and 4.2 eV. Additionally, Hirshfeld surfaces analysis was used to quantify the intermolecular interactions and to analyze intercontacts in the crystal structure. Results revealed mono-substitution molecules with ortho position will give a high impact on electronic dipole moment, thus offering a better quality NLO properties of the compounds.

Interference between the E1 and M1 Amplitudes of the Transition from the H State to C of a ThO Molecule

The systematic error in experiments concerning searching for the electric dipole moment of an electron due to the Stark interference between the E1 and M1 amplitudes of the transition from the $${{H}^{3}}{{\Delta }_{1}}$$ state to $${{C}^{1}}\Pi $$ of a ThO molecule has been calculated. The calculations show that the error is about three orders of magnitude lower than the current limitation on the electric dipole moment of electron.