Electric Dipole Components Research Articles

Sub Coulomb barrier d+ 208Pb scattering in the time-dependent basis function approach

We employ the non-perturbative time-dependent basis function (tBF) approach to study the scattering of the deuteron on 208Pb below the Coulomb barrier. We obtain the bound and discretized scattering states of the projectile, which form the basis representation of the tBF approach, by diagonalizing a realistic Hamiltonian in a large harmonic oscillator basis. We find that the higher-order inelastic scattering effects are noticeable for sub barrier scatterings with the tBF method. We have successfully reproduced experimental sub Coulomb barrier elastic cross section ratios with the tBF approach by considering only the electric dipole (E1) component of the Coulomb interaction between the projectile and the target during scatterings. We find that the correction of the polarization potential to the Rutherford trajectory is dominant in reproducing the data at very low bombarding energies, whereas the role of internal transitions of the deuteron projectile induced by the E1 interaction during the scattering becomes increasingly significant at higher bombarding energies.

Tunable interactions of quasibound states in the continuum with cavity mode in a metasurface-microcavity hybrid

All-dielectric photonic crystals or metasurfaces supporting optical bound states in the continuum (BIC) are emerging as a promising platform for the study of light-matter interactions in the strong coupling regime. However, coupling of BIC to other optical excitations is generally weak, with the coupling strength limited in the range of several tens of milli electronvolts with short decoherence time. This greatly hinders their applications in solid-base quantum information devices that require a fast information exchange rate and long coherence time. Herein, a cavity-coupling strategy is used to extend the BIC-based coupling platforms. We propose a hybrid system containing an all-dielectric metasurface embedded in an optical microcavity, demonstrating the formation of BIC-cavity polaritons in the strong coupling regime with a surprisingly large Rabi splitting over 220 meV, far beyond the strong coupling regime. A flexible tuning of BIC-cavity coupling from weak to strong coupling regime is realized by controlling the shape of dielectric element of the metasurface. Importantly, a full quantum model based on Heisenberg-Langevin formalism reveals the temporal population dynamics of the coupling system, demonstrating the ultrafast Rabi socillation within 19 fs with a long decoherence time over 200 fs. Utilizing the multipolar expansion approach combined with full wave simulations, we also investigate the coupling-induced polariton characteristics in both the weak and strong coupling regimes. We find that the electric dipole component of the BIC mode dominates in the polariton states in weak coupling regime, which dramatically changes as the system is tuned into strong coupling regime. Such a cavity-coupling strategy in the present hybrid system is expected to be of great use for enhancing BIC-based light-matter interactions for more complex hybrid nanostructures such as three-mode systems with mixing BIC-cavity-exciton interactions.

Driven electronic bridge processes via defect states in Th229 -doped crystals

The electronic defect states resulting from doping $^{229}$Th in CaF$_2$ offer a unique opportunity to excite the nuclear isomeric state $^{229m}$Th at approximately 8 eV via electronic bridge mechanisms. We consider bridge schemes involving stimulated emission and absorption using an optical laser. The role of different multipole contributions, both for the emitted or absorbed photon and nuclear transition, to the total bridge rates are investigated theoretically. We show that the electric dipole component is dominant for the electronic bridge photon. In contradistinction, the electric quadrupole channel of the $^{229}$Th isomeric transition plays the dominant role for the bridge processes presented. The driven bridge rates are discussed in the context of background signals in the crystal environment and of implementation methods. We show that inverse electronic bridge processes quenching the isomeric state population can improve the performance of a solid-state nuclear clock based on $^{229m}$Th.

Highly Porous Fluorescent Materials Based on Polymer Matrices Impregnated with Eu(dbm)3 Molecules in a Supercritical Carbon Dioxide Medium

The possibility of creating luminescent films based on highly porous polymer materials doped with the europium complex Eu(dbm)3 · H2O in a supercritical carbon dioxide medium using ethanol as a co-solvent is demonstrated. The initial polymer samples are polytetrafluoroethylene films obtained using thermal spraying or electrospinning techniques and polybenzimidazole films with foam-like structures obtained using laser irradiation. Deposition of the Eu complex in the pores of such materials (up to a few micrometers in size) leads to the appearance of bright characteristic photoluminescence (PL) in the red region, the intensity of which depends on the impregnation method and subsequent processing of the samples. An analysis of the intensity ratio between the electric dipole and magnetic dipole components of the PL spectra allow us to draw conclusions about the changes in the nearest environment of Eu3+ ions in each of the studied host materials.

All-silicon-based nano-antennas for wavelength and polarization demultiplexing.

We propose an all-silicon-based nano-antenna that functions as not only a wavelength demultiplexer but also a polarization one. The nano-antenna is composed of two silicon cuboids with the same length and height but with different widths. The asymmetric structure of the nano-antenna with respect to the electric field of the incident light induced an electric dipole component in the propagation direction of the incident light. The interference between this electric dipole and the magnetic dipole induced by the magnetic field parallel to the long side of the cuboids is exploited to manipulate the radiation direction of the nano-antenna. The radiation direction of the nano-antenna at a certain wavelength depends strongly on the phase difference between the electric and magnetic dipoles interacting coherently, offering us the opportunity to realize wavelength demultiplexing. By varying the polarization of the incident light, the interference of the magnetic dipole induced by the asymmetry of the nano-antenna and the electric dipole induced by the electric field parallel to the long side of the cuboids can also be used to realize polarization demultiplexing in a certain wavelength range. More interestingly, the interference between the dipole and quadrupole modes of the nano-antenna can be utilized to shape the radiation directivity of the nano-antenna. We demonstrate numerically that radiation with adjustable direction and high directivity can be realized in such a nano-antenna which is compatible with the current fabrication technology of silicon chips.

Electrospinning poly(l-lactic acid) piezoelectric ordered porous nanofibers for strain sensing and energy harvesting

We reported ordered porous poly(l-lactic acid) (PLLA) piezoelectric nanofibers on comb electrode for both a stain sensing and human joint motion energy harvesting. The ordered porous PLLA piezoelectric nanofibers were fabricated using electrospinning equipment. The reason for choosing this equipment was that the electric dipole component along the main carbon chain of PLLA polymer nanofibers can be polarized along the direction of alignment during the process of a direct current electric field electrospinning. When the ordered porous PLLA piezoelectric nanofibers prototype is motioned with a bending deformation, the produced charges on PLLA piezoelectric nanofibers will flow out through comb electrode for a measurement. It demonstrated that an open-circuit voltage and short-circuit current with a strain deformation angle 28.9° could reach 0.55 V and 230 pA, respectively. It concluded that the prototype could be used as a stain sensor due to the good linearity of a short-circuit current and an open-circuit voltage. Finite element calculating software (COMSOL Multiphysics) was adopted to evaluate the bending deformation and electrical performance of PLLA nanofibers. At the end, we also proved that the produced prototype worked well for harvesting human joint motion energy with a maximum peak power 19.5 nW.

Combined Molecular Dynamics and Density Functional Theory Study of Azobenzene–Graphene Interfaces

The electronic properties of graphene can be tuned in a dynamic way from physical adsorption of molecular photoswitches. Here, we first investigate the formation of 4-(decyloxy)azobenzene molecular monolayers on a single graphene layer through molecular dynamics (MD) simulations and assess the associated change in work function (WF) at the density functional theory (DFT) level. We show that the major contribution to the WF shift arises from electrostatic effects induced by the azobenzene electric dipole component normal to graphene and that the conformational distribution of the molecular switches in either their trans or cis forms can be convoluted into WF distributions for the hybrid systems. We next use this strategy to build a statistical ensemble for the work functions of graphene decorated with fluorinated azobenzene derivative designed to maximize the change in WF upon photoswitching. These findings pave the way to the possible use of photoswitchable graphene-based hybrid materials as optically con...

Magnetoelectric Dipole Antenna Arrays

A planar magnetoelectric (ME) dipole antenna array is proposed and demonstrated by both full-wave analysis and experiments. The proposed structure leverages the operation of composite right/left-handed transmission lines under balanced conditions to form high-gain magnetic radiators, combined with radial conventional electric radiators, where the overall structure is excited by a single differential feed. The traveling-wave-type nature of the proposed ME-dipole antenna enables the formation of directive arrays with high-gain characteristics and scanning capability. Peak gains of 10.84 dB and 5.73 dB are demonstrated for the electric dipole and magnetic-dipole radiation components, respectively.

Optical properties of single plasmonic holes probed with local electron beam excitation.

Similar to nanoparticles, nanoscale holes form a basic building block in a wide array of nanophotonic devices. Here we study the spectral and angular cathodoluminescence response of individual nanoholes with diameters ranging from 50 to 180 nm. Taking advantage of the deep-subwavelength excitation resolution, we find that the holes can be excited efficiently at the edge of the hole and that the response becomes stronger in the near-infrared part of the spectrum for larger holes. Using finite-difference time-domain simulations, we characterize the resonant modes inside the holes. We measure the angle-resolved cathodoluminescence response and observe strong beaming toward the side of electron beam excitation, complementary to what was shown for nanoparticles. The angular response can be explained by assuming a coherent superposition of radiating dipole moments, where the contribution of in-plane magnetic and electric dipole components increases for larger diameters.

Generation of electric and magnetic field during detonation of high explosive charges in boreholes

We present experimental results of a study of electromagnetic field generation during underground detonation of high explosive charges in holes bored in sandy loam and granite. Three components of electric field (vertical component in air and two horizontal components in the soil) and three components of the magnetic induction were recorded during the field experiments. Test conditions and physicomechanical properties of the soil exert significant influence on the parameters of electromagnetic signals generated by underground explosions with masses of 2–200 kg. The electric and magnetic field experimental data are satisfactorily described by an electric dipole model with the source embedded in layered media. We used the solution for a field produced by stationary vertical and horizontal electric dipoles placed near the interface between two layers with different conductivity. The magnitude of the field source was estimated on the basis of the records of electromagnetic signals obtained at different distances from the borehole. For an underground explosion of a TNT charge with a mass of 2 kg carried out in granite the maximum estimated value of the electric dipole component is about 10−7 C m. This estimate is more than an order of magnitude greater than that obtained for an explosion of the same mass carried out in sandy loam.

Multipole analysis of the radiation from near-field optical probes

We experimentally and theoretically analyze the radiation emitted from subwavelength-sized apertures in near-field optical probes. By decomposing the experimentally obtained radiation patterns into vector spherical waves, we describe the fields in terms of a series of multipole sources. We fit polarization-resolved angular intensity distributions, measured as far as 150 degrees from the normal, with dipole, quadrupole, and octupole radiation. We find that the magnetic and the electric dipole components are dominant but that the interference terms between dipoles and higher-order poles are not negligible. This result can be used as the basis for understanding near-field optical interactions and images.

Microwave and millimeter-wave spectra, electric dipole moment, and internal rotation effects of methyl hydroperoxide

The microwave spectrum of methyl hydroperoxide which has been investigated in the range of 12–307 GHz is dominated by the internal rotation of the OH group. The molecule exists in a gauche equilibrium configuration. Pure rotational transitions as well as much stronger torsional–rotational transitions have been assigned. A model of the overall rotation for a molecule with two strongly coupled tunneling states has been used for the analysis of all assigned transitions. Quantum-mechanical tunneling between the two equivalent gauche minima splits the ground torsional state by 448.7603(1) GHz. Additional small splittings of the microwave transitions have been attributed to the internal rotation of the CH3 group with a threefold barrier of 1120(10) cm−1. The permanent electric dipole components have been estimated from Stark splittings. Ab initio calculations of the molecular structure and of the potential functions for internal rotations of the OH and CH3 groups complement the experimental study.

Structure of the dimethylamine-sulfur dioxide complex

The microwave spectrum of the charge-transfer complex between dimethylamine and sulfur dioxide was studied with a pulsed molecular beam Fourier transform microwave spectrometer. The rotational constants (in MHz) of (CH{sub 3}){sub 2}NH{center dot}SO{sub 2} are A = 4,445.495 (3), B = 2,063.031 (1), and C = 1,752.470 (1). In addition to the normal isotopic form, the rotational spectra of the (CH{sub 3}){sub 2}NH {center dot} {sup 34}SO{sub 2}, (CH{sub 3}){sub 2}{sup 15}NH {center dot} SO{sub 2}, (CH{sub 3}){sub 2}ND {center dot} SO{sub 2}, and two (CH{sub 3}){sub 2}NH {center dot} SO{sup 18}O isotopic species were assigned. Stark effect measurements gave electric dipole components of {mu}{sub a} = 4.025 (1), {mu}{sub c} = 1.7474 (2), and {mu}{sub total} = 4.388 (1) D. The structure of this complex lacks any symmetry plane. The nitrogen lone pair points toward the S atom, nearly perpendicular to the plane of the sulfur dioxide, and one methyl group staggers the oxygen atoms. The nitrogen-to-sulfur distance of 2.34 (3) {angstrom} is about 0.08 {angstrom} longer than in the trimethylamine-SO{sub 2} complex which correlates with the relative strength of the complexes. From the dipole moment and the nitrogen nuclear quadrupole coupling constants, an upper limit is estimated formore » electron transfer from the nitrogen to the sulfur atom of 0.25 electron. Ab initio calculations also conclude that a methyl group staggers the two oxygens of SO{sub 2}.« less

A microwave spectral and ab initio investigation of O 3H 2O

Microwave spectra of O 3H 2O, O 3H 2 18O, O 3HDO, and O 3D 2O have been observed with a pulsed-beam Fabry-Perot cavity Fourier-transform microwave spectrometer. Two tunneling states, designated A 1 and A 2, are found for the normal and dideuterated isotopic forms, while only one state is observed for the O 3HDO isotope. The A 1 spectra of O 3H 2O, O 3H 2 18O, and O 3D 2O as well as the O 3HDO spectrum were fit to a Watson asymmetric top Hamiltonian, giving A = 11 960.584(5), B = 4174.036(8), and C = 3265.173(8) in MHz for O 3H 2O. The A 2 states of O 3H 2O and O 3D 2O could not be fit to a Watson Hamiltonian. This result, when combined with the large frequency splittings and the observed nuclear spin statistics for the O 3H 2O and O 3D 2O isotopic forms, suggests that there is a low barrier to internal rotation of water. The tunneling motion may also involve ozone through a concerted internal rotation of both monomer subunits. Stark effect measurements of a- and c-type transitions for O 3H 2O give the electric dipole components μ a = 1.014(2) D and μ c = 0.522(6) D. The dipole and moment of inertia data indicate that the complex has C s symmetry with water and the unique oxygen of ozone lying in the symmetry plane. This plane bisects the OOO angle of ozone. The distance between the centers of mass of ozone and water is 2.957(2) Å. From the microwave data and ab initio calculations at the MP2 6–31 G (d, p) and MP4( SDTQ) 6–31 G (d, p) level of theory it is found that the terminal oxygens of ozone are tilted toward one of the nonequivalent hydrogen atoms in water. Furthermore, the calculations reveal that O 3 and H 2O adopt an orientation within the complex that guarantees maximal stabilization by electric dipole-dipole attraction.

Cross sections for production of H(2p, 2s, 1s) by electron collisional dissociation of H2

The excitation function of H Ly-alpha from the astrophysically important dissociation of electron-excited H2 over the range 10-700 eV has been measured. The analysis predicts the cross section to energies higher than the present experimental limit, and it is found that the predicted shape is in close agreement with measured results. At 6 eV the cross section is dominated by the electric dipole first Born component, while at 100 eV the electric dipole component constitutes 73 percent of the total H(2p) cross section. The cross sections of the H(2s) and H(1s) components are calculated.

Microwave spectra and molecular conformation of methoxy difluorophosphinoxide

Two closely spaced a-type low resolution microwave band series were observed for the normal, 13C and d 3 isotopic forms of methoxy difluorophosphinoxide. The lower frequency series of the three isotopic species was found and assigned using a pulse beam Fabry—Perot cavity Fourier transform microwave spectrometer. The a- and b-type spectra of the three species were fitted to a Watson hamiltonian which gave A=4568.215(1) MHz, B=2500.471(9) MHz and C=2453.863(9) MHz for the normal species. Stark effect measurements of CH 3OP(O)F 2 led to the determination of the electric dipole component μ a =2.699(2) D and μ b =1.522(2) D. Moments of inertia and electric dipole data show that the lowest energy conformation has C s symmetry. The data are most consistent with an assignment of the observed conformer to the trans configuration. The second a-type low resolution microwave band series not observed in the pulsed beam cavity spectrometer arises from a methoxy torsional excited state fo the trans conformer or a second higher energy conformation. The absence of A–E torsional splittings in the a- and b-type spectra gives a lower limit of ∼2500 cal mol −1 for the V 3 methyl internal rotation barrier.

ChemInform Abstract: The Torsional-Rotational Spectrum and Structure of the Formaldehyde Dimer

The microwave spectra of (H2CO)2 and (D2CO)2 have been observed with a pulsed beam, Fabry–Perot cavity, Fourier transform microwave spectrometer. Both species exhibit a‐type spectra which are split by internal rotation of each monomer unit and an interchange of donor–acceptor bonding roles analogous to the water dimer. Rotational analysis of each spectrum provides the constants A=18583.(54) MHz, 1/2 (B+C)=3272.105(34) MHz, and B−C=503.92(17) MHz for (H2 CO)2 and A=14 862.1(35) MHz, 1/2 (B+C)=3030.2366(37) MHz, and B−C=490.977(18) MHz for (D2CO)2. Stark effect measurements result in derived electric dipole components μa =0.858(4) D and μb=0.027(10) D for (H2 CO)2 and μa =0.908(4) D and μb=0.095(4) D for (D2CO)2. The geometry obtained from fitting the derived moments of inertia has the planes of the two monomer units perpendicular in a nearly antiparallel orientation of the CO groups with a center‐of‐mass distance of 3.046(17) A. The shortest carbon to oxygen distance (2.98 A) and hydrogen to oxygen distanc...

The torsional–rotational spectrum and structure of the formaldehyde dimer

The microwave spectra of (H2CO)2 and (D2CO)2 have been observed with a pulsed beam, Fabry–Perot cavity, Fourier transform microwave spectrometer. Both species exhibit a-type spectra which are split by internal rotation of each monomer unit and an interchange of donor–acceptor bonding roles analogous to the water dimer. Rotational analysis of each spectrum provides the constants A=18583.(54) MHz, 1/2 (B+C)=3272.105(34) MHz, and B−C=503.92(17) MHz for (H2 CO)2 and A=14 862.1(35) MHz, 1/2 (B+C)=3030.2366(37) MHz, and B−C=490.977(18) MHz for (D2CO)2. Stark effect measurements result in derived electric dipole components μa =0.858(4) D and μb=0.027(10) D for (H2 CO)2 and μa =0.908(4) D and μb=0.095(4) D for (D2CO)2. The geometry obtained from fitting the derived moments of inertia has the planes of the two monomer units perpendicular in a nearly antiparallel orientation of the CO groups with a center-of-mass distance of 3.046(17) Å. The shortest carbon to oxygen distance (2.98 Å) and hydrogen to oxygen distance (2.18 Å) between the monomer units are indicative of a dual bond interaction to form a ring structure.

The microwave spectrum and structure of the H2O–SO2 complex

The microwave spectrum of H2O–SO2 has been observed with a pulsed beam, Fabry–Perot cavity, Fourier-transform microwave spectrometer. In addition to the normal isotopic form, we have observed the spectra of H2O–34SO2, HDO–SO2, and D2O–SO2. For the normal and dideuterated forms we observe two states with a- and c-type spectra which are split by internal rotation of the water unit, while for the 34 S and HDO species two states are observed but only the a-type spectrum was assigned. Rotational analysis of each spectrum for H2O–SO2 provides the constants A=8763.071(3) MHz, B=3819.655(2) MHz, and C=2900.899(2) MHz for the I=0 state and A=8734.268(4) MHz, B=3821.281(2) MHz, and C=2900.837(2) MHz for the I=l state, where I is the resultant proton nuclear spin. Stark effect measurements give electric dipole components μa =1.984(2) D and μc =0.488(4) D for H2O–SO2. The geometry obtained from fitting the derived moments of inertia has the planes of the two monomer units tilted approximately 45° from the parallel orientation with the oxygen atom of the water closest to the S atom of SO2, giving an S–O distance of 2.824(16) Å and a center-of-mass distance Rc.m. =2.962(5) Å. The (SO2)2 species was also produced with the same nozzle expansion conditions as used for H2O–SO2. New measurements on (SO2)2 are reported and fitted with the measurements from Nelson, Fraser and Klemperer [J. Chem. Phys. 83, 945 (1985)], providing improved rotational and centrifugal distortion constants.

Microwave spectrum and electric dipole moment of trifluoroethylene oxide

The rotational spectrum of the normal isotopic species of trifluoroethylene oxide, CHFCF 2O , was fit to a centrifugal distortion model giving rotational constants (MHz) of A = 6669.565(2), B = 3126.567(1), and C = 2652.440(1). The electric dipole moment (debyes) was determined from Stark effect measurements to be μ a = 0.402(1), μ b = 1.046(38), and μ c = 1.349(9). The experimental rotational constants are consistent with a proposed molecular structure derived from an additivity principle based upon ab initio calculations and experimental structures of related fluorinated oxiranes. Electric dipole components of trifluoroethylene oxide calculated from the proposed molecular structure and previously determined CO, CF, and HC bond moments are in reasonable agreement with the experimental values.