Electric Dipole Moments

We have measured the carrier spin dynamics in p-doped InAs/GaAs quantum dots by pumpprobe photo-induced circular dichroism and time-resolved photoluminescence experiments. We show that the hole spin dephasing is controlled by the hyperfine interaction between hole and nuclear spins. In the absence of external magnetic field, we find a characteristic hole spin dephasing time of 15 ns, in close agreement with our calculations based on dipole-dipole coupling between the hole and the quantum dot nuclei. Finally we demonstrate that a small external magnetic field, typically 10 mT instead of 200 mT for the case of electrons, quenches the hyperfine hole spin dephasing. An individual spin in a solid confined to a nanometer scale represents an ultimate quantum memory and is thus a potential candidate for the realization of spintronic and quantum information processing devices . Compared to bulk materials, the strong

This paper presents an innovative method for visualizing magnetic fields using widely available cell phone camera sensors, addressing the limitations of current methods such as solar magnetography, radio interferometry, and magnetic microscopy imaging. By leveraging the principles of the Zeeman Effect, we explore a new imaging system/method based on CMOS Sensor Data. This technique offers several advantages over existing methods, including ease of use, cost-effectiveness, and direct visualization of magnetic fields without the need for extensive data processing or specialized equipment.

This approach involves capturing short-exposure photographs of light-emitting objects influenced by magnetic fields, thereby creating interference fringes representative of the field. There are potential applications of this method in various scientific and engineering disciplines as well as strong implications for future research.

Beam dumps and fixed-target experiments have been very sensitive probes of such particles and other physics beyond the Standard Model (BSM) by considering the production of new states from the primary interaction in the beam dump. In a proton beam dump, there are many secondary interactions taking place in electromagnetic showers which may be additional production channels for pseudoscalar bosons or axion-like particles (ALPs). The target-less configuration of the MiniBooNE experiment, which collected data from 1.86 × 10 20 protons impinging directly on the steel beam dump, is an excellent test of sensitivity to these production channels of ALPs in the MeV mass region. Using the null observation of the MiniBooNE dump mode data, we set new constraints on ALPs coupling to electrons and photons produced through a multitude of channels and detected via both scattering and decays in the MiniBooNE detector volume. We find that the null result rules out parameter space that was previously unconstrained by laboratory probes in the 10-100 MeV mass regime for both electron and photon couplings. Lastly, we make the case for performing a dedicated analysis with 1.25×10 20 POT of data collected by the ArgoNeuT experiment, which we show to have complementary sensitivity and set the stage for future searches.

We study the resonant electronic excitation dynamics for ultracold atoms trapped in a deep optical lattice prepared in a Mott insulator state. Excitons in these artificial crystals are similar to Frenkel excitons in Noble atom or molecular crystals. They appear when the atomic excited state line width is smaller than the exciton band width generated by dipole-dipole coupling. When the atoms are placed within a cavity the electronic excitations and the quantized cavity mode get coupled. In the collective strong coupling regime excitations form two branches of cavity polaritons with Rabi splitting larger than the atomic and the cavity line width. To demonstrate their properties we calculate the transmission, reflection, and absorption spectra for an incident weak probe field, which show resonances at the polariton frequencies.

The result changes the mass of the lowest T = 2 level in 32 Cl substantially and improves its precision by roughly a factor of three. The new Q EC value for the superallowed β decay of 32 Ar to this level affects constraints on scalar currents via the β -ν correlation and the isospin-symmetry-breaking correction (δ C ) to the f t value for this decay. The quadratic isobaric multiplet mass equation (IMME) is found to fail for the lowest T = 2, A = 32 isobaric quintet with higher confidence than for any other isobaric multiplet; the cubic fit is excellent.

We study the dynamics of two ensembles of atoms (or equivalently, atomic clocks) coupled to a bad cavity and pumped incoherently by a Raman laser. Our main result is the nonequilibrium phase diagram for this experimental setup in terms of two parameters -detuning between the clocks and the repump rate. There are three main phases -trivial steady state (Phase I), where all atoms are maximally pumped, nontrivial steady state corresponding to monochromatic superradiance (Phase II), and amplitude-modulated superradiance (Phase III). Phases I and II are fixed points of the mean-field dynamics, while in most of Phase III stable attractors are limit cycles. Equations of motion possess an axial symmetry and a Z2 symmetry with respect to the interchange of the two clocks. Either one or both of these symmetries are spontaneously broken in various phases. The trivial steady state loses stability via a supercritical Hopf bifurcation bringing about a Z2-symmetric limit cycle. The nontrivial steady state goes through a subcritical Hopf bifurcation responsible for coexistence of monochromatic and amplitude-modulated superradiance. Using Floquet analysis, we show that the Z2-symmetric limit cycle eventually becomes unstable and gives rise to two Z2-asymmetric limit cycles via a supercritical pitchfork bifurcation. Each of the above attractors has its own unique fingerprint in the power spectrum of the light radiated from the cavity. In particular, limit cycles in Phase III emit frequency combs -series of equidistant peaks, where the symmetry of the frequency comb reflects the symmetry of the underlying limit cycle. For typical experimental parameters, the spacing between the peaks is several orders of magnitude smaller than the monochromatic superradiance frequency, making the lasing frequency highly tunable.

Excitation energy transfer processes and mechanism in C-PC hexamer have been studied in detail by picosecond time-resolved fluorescencs isotropic and anisotropic spectroscopy methods. The experimental results show that there are two types of principal channels, with large probability or amplitude, for linking two trimers viam↔m and s↔s energy transfer pathways, the energy-transfer time constants of them are about 20 and

Thin ®lms of many molecular materials are considered `amorphous' because they possess no detectable long-range order. However, we show that the ¯uorescence spectrum of polar molecules may shift due to the formation of ordered polar domains within an otherwise amorphous ®lm. A model is derived to explain this shift and the associated quenching of luminescence as domains are formed. We demonstrate that the inclusion of dipole±dipole intermolecular correlations has a signi®cant eect on calculations of the electronic properties of organic amorphous thin ®lms.

A new method is developed to calculate the optical tensors of large systems based on available wave function correlation approaches ͑e.g., the coupled cluster ansatz͒ in the framework of the incremental scheme. The convergence behaviors of static first-and second-order polarizabilities with respect to the order of the incremental expansion are examined and discussed for the model system Ga 4 As 4 H 18 . The many-body increments of optical tensors originate from the dipole-dipole coupling effects and the corresponding contributions to the incremental expansion are compared among local domains with different distances and orientations. The weight factors for increments of optical tensors are found to be tensorial in accordance with the structural symmetry as well as the polarization and the external electric field directions. The long-term goal of the proposed approach is to incorporate the sophisticated molecular correlation methods into the accurate wave function calculation of optical properties of large compounds or even crystals.

Localized proton MR spectra of mouse skeletal muscle obtained at 7 T show dipole-dipole coupling effects for creatine and putative taurine resonances and for the lactate methine signal. These effects are independent of the presence of creatine kinase. The intensity of the methylene 1 H resonance of creatine is not different between wild-type and creatine kinase deficient mice, which have a lower phosphocreatine content. 1 H-MR spectra acquired post-mortem from wild-type mouse skeletal muscle parallel to B 0 show a linewidth decrease for the methyl resonance of creatine and a 20% signal intensity loss for its methylene peak concurrent with the total breakdown of phosphocreatine as observed by 31 P-MR spectroscopy. However, with the muscle at the magic angle no changes in the appearance and intensity of creatine (and taurine) resonances are observed. These results indicate that the changes observed for creatine resonances are related to altered dipolar couplings and that the intensity of the methylene peak does not necessarily reflect muscular phosphocreatine content. Magn Reson Med 43:517-524, 2000.

This paper presents a groundbreaking discovery in atomic physics, where atoms are directly visualized through photonic projections using high-intensity LED illumination and smartphone camera sensors. The technique provides unprecedented insights into the structure and dynamics of atoms, revealing concentric proton rings, electron orbital patterns, and a rapidly moving central core. This discovery has enabled the development of a unified theory of space compression, proposing that matter emerges from the compression of neutral mass (space) at specific ratios. By integrating observations with Russell's wavelength-spiral design of the periodic table, we establish mathematical relationships between nuclear magnetic dipole moments, atomic voltage, and chemical bonding. The framework accurately predicts bond properties, molecular geometries, and material characteristics, with successful validation against experimental data. This unified approach offers potential solutions to fundamental physics puzzles, such as the unification of forces, the nature of gravity, and the origin of matter-antimatter asymmetry. The paper concludes with applications for novel materials design and implications for our understanding of quantum phenomena.

This paper presents a groundbreaking discovery in atomic physics, where atoms are directly visualized through photonic projections using high-intensity LED illumination and smartphone camera sensors. The technique provides unprecedented insights into the structure and dynamics of atoms, revealing concentric proton rings, electron orbital patterns, and a rapidly moving central core. This discovery has enabled the development of a unified theory of space compression, proposing that matter emerges from the compression of neutral mass (space) at specific ratios. By integrating observations with Russell's wavelength-spiral design of the periodic table, we establish mathematical relationships between nuclear magnetic dipole moments, atomic voltage, and chemical bonding. The framework accurately predicts bond properties, molecular geometries, and material characteristics, with successful validation against experimental data. This unified approach offers potential solutions to fundamental physics puzzles, such as the unification of forces, the nature of gravity, and the origin of matter-antimatter asymmetry. The paper concludes with applications for novel materials design and implications for our understanding of quantum phenomena.

This paper presents a groundbreaking discovery in atomic physics, where atoms are directly visualized through photonic projections using high-intensity LED illumination and smartphone camera sensors. The technique provides unprecedented insights into the structure and dynamics of atoms, revealing concentric proton rings, electron orbital patterns, and a rapidly moving central core. This discovery has enabled the development of a unified theory of space compression, proposing that matter emerges from the compression of neutral mass (space) at specific ratios. By integrating observations with Russell's wavelength-spiral design of the periodic table, we establish mathematical relationships between nuclear magnetic dipole moments, atomic voltage, and chemical bonding. The framework accurately predicts bond properties, molecular geometries, and material characteristics, with successful validation against experimental data. This unified approach offers potential solutions to fundamental physics puzzles, such as the unification of forces, the nature of gravity, and the origin of matter-antimatter asymmetry. The paper concludes with applications for novel materials design and implications for our understanding of quantum phenomena.

The study investigates transient electromagnetic (EM) radiation in the near-field zone of a system of electric dipoles and the usage of the plane wave spectrum (PWS) concept for extraction of a 3-D field from 2-D measurements. Both aspects are important in the modelling and characterisation of radiated emissions in electromagnetic compatibility applications, which are extended here to time domain. Analytical expressions for a set of dipoles excited by short-duration Gaussian pulses, which in the author's approach are used to model EM radiation, are presented and implemented into a Matlab program to calculate the time-dependent distributions of the three electric field components E x (t), E y (t), E z (t). These results are then used to verify the new technique of extraction of the time-domain component E z (t) of the electric field from measurements of the two other components, E x (t) and E y (t). The details of the technique, based on PWS method applied to the time domain, are presented. Very good agreement between the extracted and analytically calculated fields has been achieved. Further verification and comparison has been done by the simulation in the time domain of the system of dipoles using commercial 3-D EM software.

The propagation behaviors, which include the carrier-envelope phase, the area evolution and the solitary pulse number of few-cycle pulses in a dense two-level medium, are investigated based on full-wave Maxwell-Bloch equations by taking Lorentz local field correction (LFC) into account. Several novel features are found: the difference of the carrier-envelope phase between the cases with and without LFC can go up to π at some location; although the area of ultrashort solitary pulses is lager than 2π, the area of the effective Rabi frequency, which equals to that the Rabi frequency pluses the product of the strength of the near dipole-dipole (NDD) interaction and the polarization, is consistent with the standard area theorem and keeps 2π; the large area pulse penetrating into the medium produces several solitary pulses as usual, but the number of solitary pulses changes at certain condition.

STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of populations between quantum states. A particularly interesting feature is the fact that the coupling between the initial and the final quantum states is via an intermediate state, even though the lifetime of the latter can be much shorter than the interaction time with the laser radiation. Nevertheless, spontaneous emission from the intermediate state is prevented by quantum interference. Maintaining the coherence between the initial and final state throughout the transfer process is crucial. STIRAP was initially developed with applications in chemical dynamics in mind. That is why the original paper of 1990 was published in The Journal of Chemical Physics. However, from about the year 2000, the unique capabilities of STIRAP and its robustness with respect to small variations in some experimental parameters stimulated many researchers t...

We develop three methods to invert induced polarization (IP) data. The foundation for our algorithms is an assumption that the ultimate effect of chargeability is to alter the effective conductivity when current is applied. This assumption, which was first put forth by Siegel and has been routinely adopted in the literature, permits the IP responses to be numerically modeled by carrying out two forward modelings using a DC resistivity algorithm. The intimate connection between DC and IP data means that inversion of IP data is a two‐step process. First, the DC potentials are inverted to recover a background conductivity. The distribution of chargeability can then be found by using any one of the three following techniques: (1) linearizing the IP data equation and solving a linear inverse problem, (2) manipulating the conductivities obtained after performing two DC resistivity inversions, and (3) solving a nonlinear inverse problem. Our procedure for performing the inversion is to div...

The determination of the dielectric properties of polar liquids by computer simulation has, in the past, presented both conceptual and computational difficulties. Many of the conceptual problems have now been at least partially resolved, yet the accurate calculation of the dielectric response for a highly polar liquid remains a major computational task. The usual means of obtaining the static dielectric constant, R, is through the fluctuations in the total dipole moment of the system. In this paper we describe an alternate approach which relies upon the long-range asymptotic behaviour of the dipole-dipole correlations in order to determine g. It requires that a rather large simulation cell be employed, in the present case samples of 4000 particles. Molecular dynamics simulations have been performed for a highly polar fluid composed of dipolar soft spheres in which the dipole-dipole interactions have been evaluated using the Ewald summation technique. Results for the static dielectric constant are reported and compared with previous calculations. The microscopic structure is examined in detail with particular attention being paid to the effects of boundary conditions and numerical implementation. We also consider whether the current understanding of these systems can in fact account for the behaviour observed.

We propose the Bose-Einstein condensation (BEC) and superfluidity of quasi-two-dimensional (2D) spatially indirect magnetobiexcitons in a slab of superlattice with alternating electron and hole layers consisting from the semiconducting quantum wells (QWs) and graphene superlattice in high magnetic field. The two different Hamiltonians of a dilute gas of magnetoexcitons with a dipole-dipole repulsion in superlattices consisting of both QWs and graphene layers in the limit of high magnetic field have been reduced to one effective Hamiltonian a dilute gas of two-dimensional excitons without magnetic field. Moreover, for N excitons we have reduced the problem of 2N × 2 dimensional space onto the problem of N × 2 dimensional space by integrating over the coordinates of the relative motion of an electron (e) and a hole (h). The instability of the ground state of the system of interacting two-dimensional indirect magnetoexcitons in a slab of superlattice with alternating electron and hole layers in high magnetic field is established. The stable system of indirect quasi-two-dimensional magnetobiexcitons, consisting of pair of indirect excitons with opposite dipole moments is considered. The density of superfluid component ns(T ) and the temperature of the Kosterlitz-Thouless phase transition to the superfluid state in the system of two-dimensional indirect magnetobiexcitons, interacting as electrical quadrupoles, are obtained for both QW and graphene realizations.

Variations of soil structure is significant for the understanding of water and gas transfer in soil profiles. In the context of arable land, soil structure can be compacted due to either agriculture operation (wheel tracks), or hardsetting and crusting processes. As a consequence, soil porosity is reduced which may lead to decrease water infiltration and to anoxic conditions. Porosity can be increased by cracks formation due to swelling and shrinking phenomenon. We present here a laboratory experiment based on soil electrical characteristics. Electrical resistivity allows a non destructive three dimensional and dynamical analysis of the soil structure. Our main objective is to detect cracks in the soil. Cracks form an electrical resistant object and the contrast of resistivity between air and soil is large enough to be detected. Our sample is an undisturbed soil block 240mm*170mm*160mm with an initial structure compacted by wheel traffic. Successive artificial cracks are generated. Electrodes built with 2 mm ceramic cups permit a good electrical contact at the soil surface whatever its water content. They are installed 15 mm apart and the electrical resistivity is monitored using a dipole-dipole and wenner multi-electrodes 2D imaging method which gives a picture of the subsurface resistivity. The interpreted resistivity sections show the major soil structure. The electrical response changes with the cracks formation. The structure information extracted from the electrical map is in good agreement with the artificially man-made cracks. These first results demonstrate the relevance of high resolution electrical imaging of the soil profile. Further experiments need to be carried out in order to monitor natural soil structure evolution during wetting-drying cycles.

The present study aimed to delineate subsurface features and identify prospective metallic mineral deposits in the Adıyaman-Besni area, situated within the Southeastern Anatolian Thrust Belt of Turkey. This region, characterized by ophiolitic mélanges and volcanic massive sulfide (VMS) deposits in its geological framework, possesses significant mineralization potential, encompassing copper, lead, and various other sulfide minerals.
Utilizing the combined methodologies of Induced Polarization (IP) and Electrical Resistivity Tomography (ERT), a comprehensive electrical mapping of the subsurface structures was conducted, revealing that mineralized zones had low resistivity and high chargeability. The
findings indicate that the combined use of IP and ERT techniques yields excellent precision in accurately delineating the features of sulfide mineralization and the peripheries of mineral deposits. This study offers fundamental data for the economic assessment of prospective mineral deposits in the Adıyaman-Besni region and underscores the benefits of IP and ERT techniques in subsurface mapping and mineralization delineation investigations. The mineralized zone has low resistivity (< 50 ohm-m) and strong chargeability (> 30 ms), according to geophysical tests. It also offers a methodological framework for subsequent mineral exploration research in analogous geological formations.

The simultaneous interpretation of a suite of dipole-dipole and dipole-CSA cross-correlation rates involving the backbone nuclei 13Ca, 1Ha,13CO, 15N and 1HN can be used to resolve the ambiguities associated with each individual cross-correlation rate. The method is based on the transformation of experimental cross-correlation rates via calculated values based on standard peptide plane geometry and solid-state 13CO CSA parameters into

Structural and thermodynamic properties of spherical particles carrying classical spins are investigated by Monte Carlo simulations. The potential energy is the sum of short range, purely repulsive pair contributions, and spin-spin interactions. These last are of the dipole-dipole form, with however, a crucial change of sign. At low density and high temperature the system is a homogeneous fluid of weakly interacting particles and short range spin correlations. With decreasing temperature particles condense into an equilibrium population of free floating vesicles. The comparison with the electrostatic case, giving rise to predominantly one-dimensional aggregates under similar conditions, is discussed. In both cases condensation is a continuous transformation, provided the isotropic part of the interatomic potential is purely repulsive. At low temperature the model allows us to investigate thermal and mechanical properties of membranes. At intermediate temperatures it provides a simple model to investigate equilibrium polymerization in a system giving rise to predominantly twodimensional aggregates.

To search the electric dipole moment was proposed to use polarized protons at the so-called ”magic” momentum of 0.7 GeV/c in an electric storage ring [1]. For studying beam dynamics in electrostatic rings different computational methods can be used. We used differential algebra methods realized in COSY Infinity and integrating program with symplectic Runge-Kutta methods. These methods were observed and compared for orbital and spin motion.

Several known gas seep sites along the Hikurangi Margin off the east coast of New Zealand were surveyed by marine controlled source electromagnetic (CSEM) experiments. A bottom-towed electric dipole-dipole system was used to reveal the occurrence of gas hydrate and methane related to the seeps. The experiments were part of the international multidisciplinary research program "New Vents" carried out on German R/V Sonne in 2007 (cruise SO191) to study key parameters controlling the release and transformation of methane from marine cold vents and shallow gas hydrate deposits. Two CSEM lines have been surveyed over known seep sites on Opouawe Bank in the Wairarapa region off the SE corner of the North Island. The data have been inverted to sub-seafloor apparent resistivity profiles and one-dimensional layered models. Clearly anomalous resistivities are coincident with the location of two gas seep sites, North Tower and South Tower on Opouawe Bank. A layer of concentrated gas hydrate within the uppermost 100 m below the seafloor is likely to cause the anomalous resistivities, but free gas and thick carbonate crusts may also play a role. Seismic data show evidence of fault related venting which may also indicate the distribution of gas hydrates and/or authigenic carbonate. Geochemical profiles indicate an increase of methane flux and the formation of gas hydrate in the shallow sediment section around the seep sites. Takahe is another seep site in the area where active venting, higher heat flow, shallow gas hydrate recovered from cores, and seismic fault planes, but only moderately elevated resistivities have been observed. The reasons could be a) the gas hydrate concentration is too low, even though methane venting is evident, b) strong temporal or spatial variation of the seep activity, and c) the thermal anomaly indicates rather temperature driven fluid expulsion that hampers the formation of gas hydrate beneath the vent.

We explore a new class of axion models in which some, but not all, of the left-handed quarks have a Peccei-Quinn symmetry. These models are potentially afflicted by flavour changing neutral currents. We derive the bounds on the Peccei-Quinn symmetry-breaking scale from bounds on the K + → π + a branching ratio, showing that in some cases they are even stronger than the astrophysical ones, but still not strong enough to kill off the models. 1 One of the most persistent problems in particle physics is the so called strong CP problem. The CP invariance of the strong interactions can, in principle, be spoiled by the addition of the allowed ‘θ-term ’ [1] Lθ = θ g2 s

An isoenthalpic-isobaric molecular dynamics simulation was used to study the structural properties of crystalline InSb, based on an effective interaction potential. The interaction potential consists of an effective pair potential which takes into account atomic-size effects and charge-charge, charge-dipole, dipole-dipole, and three-body interactions, the last needed to describe bond bending and bond stretching. The system consists of 1000 particles ͑500 In and 500 Sb͒ initially in a cubic box of side Lϭ32.397 Å. The simulation of the pressure-induced structural transformation was done at fixed temperature, with the external pressure increasing in steps of 0.2 GPa up to 6.0 GPa. The phase transformation from fourfold-coordinated zinc-blende to sixfoldcoordinated orthorhombic structure is successfully reproduced at the correct experimental value of ϳ3 GPa. Pair distribution function, coordination number, volume change, and bond angle distributions are presented and compared with experimental available data.

During bacterial chemotaxis, the histidine autokinase CheA interacts with the chemotaxis receptors with the help of the coupling protein CheW. The CheA-CheW interaction is typical of many macromolecular complexes where protein-protein interactions play an important role. In this case a relatively small protein, CheW (18 kDalton), becomes part of a much larger complex. Here we describe a new method to

Particle accelerators have been widely used for physics research since the early 20 th century and have greatly progressed both scientifically and technologically since then. To gain an insight into the physics of elementary particles, one accelerates them to very high kinetic energy, let them impact on other particles, and detect products of the reactions that transform the particles into other particles. It is estimated that in the post-1938 era, accelerator science has influenced almost 1/3 of physicists and physics studies and on average contributed to physics Nobel Prize-winning research every 2.9 years [1]. Colliding beam facilities which produce high-energy collisions (interactions) between particles of approximately oppositely directed beams did pave the way for progress since the 1960's. Discussion below mainly follows recent publication [2]. Twenty nine colliders reached operational stage between the late 50's and now. The energy of colliders has been increasing over the years as demonstrated in Fig.1. There, the triangles represent maximum CM energy and the start of operation for lepton (usually, e+e-) colliders and full circles are for hadron (protons, antiprotons, ions, proton-electron) colliders. One can see that until the early 1990's, the CM energy on average increased by a factor of 10 every decade and, notably, the hadron colliders were 10-20 times more powerful. Since then, following the demands of high energy physics, the paths of the colliders diverged to reach record high energies in the particle reaction. The Large Hadron Colider (LHC) was built at CERN, while new e+e-colliders called "particle factories" were focused on detail exploration of phenomena at much lower energies.

In response to a request from the CERN Scientific Policy Committee (SPC), the machine parameters and expected luminosity performance for several proposed post-LHC collider projects at CERN are compiled: three types of hadron colliders (HL-LHC upgrade, FCC-hh and HE-LHC), a circular lepton collider (FCC-ee), a linear lepton collider (CLIC), and three options for lepton-hadron colliders (LHeC, HE-LHeC, and FCC-eh). Particular emphasis is put on availability, physics run time, and efficiency. The information contained in this document was presented at the SPC Meeting of September 2018. It will serve as one of the inputs to the 2019/20 Update of the European Strategy for Particle Physics.

We propose a strategy based on the combination of experimental NHN/CαHα dipole/dipole cross‐correlated relaxation rates and chemical shift analysis for the determination of Ψ torsion angles in proteins. The method allows the determination of a dihedral angle that is not easily accessible by nuclear magnetic resonance (NMR). The measurement of dihedral angle restraints can be used for structure calculation, which is known to improve the quality of NMR structures. The method is of particular interest in the case of large proteins, for which spectral assignment of the nuclear Overhauser effect spectra, and therefore straightforward structural determination, is out of reach. One advantage of the method is that it is reasonably simple to implement, and could be used in association with other methods aiming at obtaining structural information on complex systems, such as residual dipolar coupling measurements. An illustrative example is analyzed in the case of the 30‐kDa protein 6‐phosphog...

, OH-We study the dependence of the excitation transfer rate between coupled quantum dots (QDs) on the polarization and the intensity of the exciting light. We use the density matrix to study the dynamics of the luminescence polarization of the QDs [1]. We consider a detailed description of the band edge fine structure of the exciton in the QDs based on an effective mass description with eight exciton levels [2]. The QDs are coupled via the dipole-dipole Forster-like interaction with realistic, experimentrelevant parameters. We investigate the dependence of the luminescence polarization on the polarization of the exciting light and how such measurement give us information about the angular orientation of the excited dipole in the donor dot and the transferred dipole in the acceptor dot. We also study the dynamics of the QD system in the case of multiple-excitons, obtained by increasing the intensity of the exciting light. In this case, the coupling between the QDs includes all the possible interactions between the excitons. The exchange interactions are found to strongly influence the energy transfer rate and affect the resulting polarization. Supported by The Indiana 21

We elaborate on an operator approach to effective medium theory for homogenization of the periodic multilayered structures composed of nonmagnetic isotropic materials, which is based on equating the spatial evolution operators for the original structure and its effective alternative. We show that the zeroth-, first-, and second-order approximations of the operator effective medium theory correspond to electric dipoles, chirality, and magnetic dipoles plus electric quadrupoles, respectively. We discover that the spatially dispersive bianisotropic effective medium obtained in the second-order approximation perfectly replaces a multilayered composite and does not suffer from the effective medium approximation breakdown that happened near the critical angle of total internal reflection found previously in the conventional effective medium theory. We establish the criterion of the validity of the conventional effective medium theory depending on the ratio of unit-cell length to the wavelength, the number of unit cells, and the angle of incidence. The operator approach to effective medium theory is applicable for periodic and nonperiodic layered systems, being a fruitful tool in the fields of metamaterials and subwavelength nanophotonics.

A docking approach for molecular mechanics optimization of P-cyclodextrin complexes is described. Because of the specific geometry of the cyclodextrins and the class of guests (relatives of tert-butyl benzene), the guest molecule is moved along a vector going through the middle of the cavity. This vector is perpendicular to the mean plane of the a&al oxygen atoms that link the glucose units. At each step along this vector, the geometry of the bimolecular assembly was optimized to give a minimum in the molecular mechanics steric energy. As expected, the energy decreases as the guest molecule enters the cyclodextrin cavity, and again increases as the guest exits from the other side of the cavity. Rotation of the guest within the cavity prior to energy minimization did not result in lower energies; the minimization process found the best rotational orientation of the guest. On the other hand, it was necessary to drive the guest along the vector; the energy minimization process did not pull the guest into an optimal depth of penetration into the cavity. The binding energies calculated at two different dielectric constants were almost identical, indicating that the complex formation is stabilized by dispersive or Van der Waals forces and not electrostatic (dipole-dipole or hydrogen bonding) forces.

The effect that may be exerted by an interatomic near dipole-dipole interaction upon optical transient processes in dense resonance media is analyzed. The behavior of the macroscopic polarization after a one-pulse excitation of a dense ensemble of two-level atoms is considered. It is shown that the free polarization signal is of oscillatory nature, with the oscillation frequency varying in time and being dependent on the dipole-dipole interaction constant, the intensity and duration of the exciting pulse, and the detuning of its carrier frequency from the resonance. The free polarization signal decay, which depends on the magnitude and sign of the sum of the detuning of the exciting pulse carrier frequency from the resonance and the Lorentz frequency, may obey either a power or an exponential law. The signal decay rate is determined not only by the inhomogeneous broadening, but also by the ratio of the above parameters. The peculiarities of echo-responses under one-or two-pulse excitation conditions are studied.

One of the most stringent requirements during the energy ramp of the Large Hadron Collider (LHC) is to have a constant ratio between dipole-quadrupole and dipole-dipole field so as to control the variation of the betatron tune and of the beam orbit throughout the acceleration phase, hence avoiding particle loss. To achieve the nominal performance of the LHC, a maximum variation of ±0.003 tune units can be tolerated. For the commissioning with low intensity beams, acceptable bounds are up to 30 times higher. For the quadrupole-dipole integrated field ratio, the above requirements translate in the tight windows of 6 ppm and 180 ppm, while for dipole differences between sectors the acceptable error is of the order of 10-4. Measurement and control at this level are challenging. For this reason we have launched a dedicated measurement R&D to demonstrate that these ratios can be measured and controlled within the limits for machine operation. In this paper we present the techniques developed to power the magnets during the current ramps, the instrumentation and data acquisition setup used to perform the tracking experiments, the calibration procedure and the data reduction employed.

We study Bromine and Chlorine chemisorption on a Ag(100) surface, using a lattice-gas model and the quantum-mechanical Density Functional Theory (DFT) method. In this model the Br and Cl ions adsorb at the fourfold hollow sites of the Ag(100) surface, which can be represented by a square lattice of adsorption sites. Five different coverages were used for each kind of adsorbate. For each adsorbate and coverage, we obtained the minimum-energy configuration, its energy, and its charge distribution. From these data we calculated dipole moments, lateral interaction energies, and binding energies. Our results show that for Br the lateral interactions obtained by fitting to the adsorption energies obtained from the DFT calculation are consistent with long-range dipoledipole lateral interactions obtained using the dipole moments calculated from the DFT charge distribution. For Cl we found that, while the long-range dipole-dipole lateral interactions are important, short-range attractive interactions are also present. Our results are overall consistent with parameter estimates previously obtained by fitting room-temperature Monte Carlo simulations to electrochemical adsorption isotherms [I.

We studied Br and Cl chemisorbed on a Ag(100) surface, using a latice-gas model and the Density Functional Theory (DFT) method. In this model the Br and Cl ions adsorb at the fourfold hollow sites of the Ag(100) surface, which yields a square lattice of adsorption sites. Five different coverages for each kind of adsorbate were calculated. For each adsorbate and coverage, we obtained the minimum-energy configuration, its energy, and its charge distribution. From these data we calculated dipole moments, lateral interaction energies, and binding energies. Our results showed that for Br the lattice-gas model obtained by fitting to the adsorption energies from the DFT calculation is consistent with long-range dipole-dipole lateral interactions using the dipole moments calculated from DFT charge distribution. For Cl we found less consistency, which indicates that long-range dipole-dipole interactions are not sufficient to describe the Chlorine system.

FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO-and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3 Á/21G1 levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole Á/dipole and hydrogen bonding mechanisms.

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly helium-3) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY (Cooler Synchrotron, Forschungszentrum J\&quot;ulich) activities that demonstrate technical feasibility. Achievements to date include reduced polarisation measurement errors, long horizontal-plane polarisation lifetimes, an...

We present an overview of solid-state NMR studies of endohedral H 2-fullerene complexes, including 1 H and 13 C NMR spectra, 1 H and 13 C spin relaxation studies, and the results of 1 H dipole-dipole recoupling experiments. The available data involves three different endohedral H 2-fullerene complexes, studied over a wide range of temperatures and applied magnetic fields. The symmetry of the cage influences strongly the motionally-averaged nuclear spin interactions of the endohedral H 2 species, as well as its spin relaxation behaviour. In addition, the non-bonding interactions between fullerene cages are influenced by the presence of endohedral hydrogen molecules. The review also presents several pieces of experimental data which are not yet understood, one example being the structured 1 H NMR lineshapes of endohedral H 2 molecules trapped in highly symmetric cages at cryogenic temperatures. This review demonstrates the richness of NMR phenomena displayed by H 2-fullerene complexes, especially in the cryogenic regime.

Angeles-Crystals of dipolar molecular rotors may display novel phenomena with applications to memories and signal processing. We report on the characterization of crystals of synthesized dipolar molecular rotors. Crystal design provides for control over dipole moment, distance between dipoles, and barriers to rotation. We have previously reported characterization of the rotational potential for crystals with an asymmetric two-well potential in which the asymmetry was caused by steric interactions between the dipole and its surrounding crystal cage. In an effort to isolate the effects of rotor-rotor interactions, we now report on a system with a larger dipole moment and a sterically symmetric rotational potential. Dielectric spectroscopy results show that the two-well potential in this system is still asymmetric. Two models for the asymmetry are investigated through Monte Carlo simulations. In the first, we suppose that the asymmetry is caused by dipole-dipole interactions between rotors and evaluate the interaction strength needed to reproduce the observations. In the second, we consider the effects of a quenched random field.

High-resolution electron energy-loss spectroscopy (HREELS) has been used to investigate the vibrational properties of the newly discovered, well-ordered oxygen (1×1) overlayer on Ru(001). The totally symmetric RuMO stretch has been mapped out along the C 9-K 9-M 9-K 9 direction of the surface Brillouin zone (SBZ). The stretching mode exhibits a strong downward dispersion of about 100 cm−1 along C 9-K 9 starting at 660 cm−1, with a subsequent upward dispersion along K 9-M 9. The dispersion observed for small k d is explained by dominating long-range dynamical dipole-dipole coupling. From comparisons of experimental data in the vicinity of the C 9 point with calculations for dipole-dipole coupling, the frequency of the isolated oscillator (singleton frequency), as well as the vibrational and electronic polariziabilities, can be estimated to be 598 cm−1, 0.8 Å 3 and 1.7 Å 3, respectively. However, the short-range interactions deviate significantly from dynamical dipole-dipole interactions as is documented by the discrepancy between the calculated and the observed dispersion between K 9 and M 9 .

The relaxation of polarization in time is studied for a two-dimensional dipolar lattice. Simulations are carried out integrating numerically the ordinary differential equations that result from considered dipole-dipole and dipole external field interaction for each dipole in a plane dipole arrangement. A potential law is found in the simulation of relaxation of polarization in time domain, in good agreement with experimental evidence. The influence of several parameters in system response is discussed. A hysteresis loop of polarization was obtained, showing ferroelectric behavior of the model.