Off-resonance Region Research Articles

O(αs) CORRECTIONS TO B→ Xse+e-DECAY IN THE 2HDM

O(αs) QCD corrections to the inclusive B→Xse+e-decay are investigated within the two-Higgs doublet extension of the standard model (2HDM). The analysis is performed in the so-called off-resonance region; the dependence of the obtained results on the choice of the renormalization scale is examined in details. It is shown that O(αs) corrections can suppress the B→Xse+e-decay width up to 1.5–3 times (depending on the choice of the dilepton invariant mass s and the low-energy scale μ). As a result, in the experimentally allowed range of the parameter space, the relations between the B→Xse+e-branching ratio and the new physics parameters are strongly affected. It is also found that though the renormalization scale dependence of the B→Xse+e-branching is significantly reduced, higher order effects in the perturbation theory can still be non-negligible.

Third-order optical nonlinearity of chlorin derivatives

Second-order molecular hyperpolarizabilities (γ) of four tetraphenylchlorin derivatives were measured by the Z -scan technique at 784 nm in the off-resonant region and the enhancement in the hyperpolarizabilities of these derivatives in comparison to the regular porphyrins with the same external side-groups is explained on the basis of the difference in their Q-band oscillator strengths.

Spin-resolved FeL3M2,3M2,3andL3M2,3VAuger transitions on and off resonance by excitation with linearly polarized photons

Spin polarized Fe ${L}_{3}{M}_{2,3}{M}_{2,3}$ and ${L}_{3}{M}_{2,3}V$ Auger-electron spectra were measured and calculated using on-resonance excitation energies of linearly polarized photons (at the ${2p}_{3/2}$ threshold) as well as in the off-resonance region. Both the intensity distribution and the spin polarization in the experimentally obtained Auger spectra are explained by means of the theoretical model taking into account spin-orbit splitting of core levels and exchange interaction of the core states with the polarized valence band. Different contributions to the Auger spin polarization of both $\mathrm{CCC}$ (Fe ${L}_{3}{M}_{2,3}{M}_{2,3})$ and $\mathrm{CCV}$ (Fe ${L}_{3}{M}_{2,3}V)$ Auger spectra are discussed. Auger electron spin polarization is positive by transitions to the singlet final two-hole states and is increased with increasing core state-valence state exchange interaction, whereas for the triplet final states the opposite behavior is found.

Dynamic analysis of piezoceramic actuation effects on plate vibrations

This paper presents a simulation model for the active vibration control of a rectangular plate using piezoceramic elements of arbitrary shape. Experiments using multiple PZT patches were carried out to validate the model. An analysis was then undertaken to determine the dynamic effect of the piezoactuators. Numerical results showed that piezoactuators enhance the modal coupling of the structure under certain circumstances. Special attention should be paid to higher-order modes in both simulation and the development of active control strategies. Actuators of different shapes have been tested to show their influence on the dynamic behaviour of the structure. It was noted that actuators shapes affect the structure more in off-resonance regions than near resonance. This effect however remains weak as long as the actuators possess the same area and do not possess significantly different width to length dimensions.

A-Si:H film on side-polished fiber as optical polarizer and narrow-band filter

An optical waveguide structure consisting of side-polished single-mode fiber covered with thin a-Si:H planar waveguide is studied as a channel-dropping narrow-band filter and fiber-optic polarizer. Spectral and polarization characteristics of the structure are measured in the wavelength region of 600–1600 nm, for the different values of the a-Si:H film thickness and the superstrate refractive index. The FWHM of the filter is about 8 nm for the asymmetric waveguide and 10 nm for the symmetric one. The discrimination of the resonance minima for two polarizations varies from several tens for the symmetric PWG up to several hundreds of nanometers for the asymmetric PWG. The optical losses in the off-resonance region are less than 0.3 dB. The measured value of the extinction coefficient of the fiber-optical polarizer is 32.5 dB.

Cyclotron resonance of interface magnetopolarons at finite temperatures

Taking into account the interaction of an electron with interface optical phonons as well as bulk longitudinal optical phonons, we study the cyclotron resonance of magnetopolarons at the interfaces of polar crystals. We consider both the absorption and emission processes in our calculation using the Green's function method at finite temperatures. Consequently, different temperature characteristics of the cyclotron resonance mass and resonance frequency are found on either side of the off-resonance magnetic field region.

Optical force on a sphere caused by the evanescent field of a Gaussian beam; effects of multiple scattering

We examine theoretically the optical force exerted on a dielectric sphere by the evanescent field of a Gaussian beam, where multiple scattering of light between the sphere and the prism substrate is considered. We derive first an expression of the nth order field ( n ≥ 1) that is scattered by the sphere and we then formulate the optical force due to the scattered fields up to nth order. Numerical results show that the effect of multiple scattering up to third order exerted on the optical force is within the extent of ∼ 10% in resonance regions but it is negligible in off-resonance regions.

Vibration Characteristics of Sandwich Beams Partially and Fully Treated with Electro-Rheological Fluid

This experimental study investigated the vibrational properties of a sandwiched beam clamped at both ends and fully or partially treated with an electro-rheological (ER) fluid layer. Frequency response function curves were obtained and analysed in the frequency range between 10 to 1000 Hz. Three factors were investigated for its effect on the ER sandwich beam system, i.e., electric field strength, length of the ER fluid layer and applied excitation gain. It was found that the electric field strength has little effect on loss factors and resonant frequencies of the fully treated beam, except for reduced vibration in some off-resonance regions. For the partially treated beam, the length of the ER fluid layer has a significant effect on resonant frequencies, but little effect on loss factors. As the length of the ER fluid layer increases, the resonant frequencies become higher in the entire frequency range considered. It was also observed that both partially and fully treated ER sandwich beams are almost linear systems, i.e., when different excitation gain levels are applied to the beams, the frequency response function curves are unchanged.

Trilepton signals from chargino - neutralino production at the CERN pp-collider in a supersymmetric left - right model

We study production of charginos and neutralinos at the CERN large hadronic collider () within the framework of the left - right supersymmetric (LRS) model and compare it with the minimal supersymmetric standard model (MSSM) and with the background signal. We investigate the possibility of detecting trilepton signals for in the on- and off-resonance regions. The interest in such a calculation is not merely that it would give larger branching ratios than the MSSM, but that it allows exploration of significant regions of left - right supersymmetry parameter space beyond the reach of the MSSM model.

Radiative dielectronic recombination and correlated processes

A new quasi-resonant radiative dielectronic recombination (RDR) process is formulated as an off-shell extension of the dielectronic recombination. It is an electron-ion recombination process in which dielectronic-excitation capture is accompanied by simultaneous radiation emission, and can occur at all continuum energies of the electron being captured. The RDR can be the dominant mode of recombination at off-resonance energy regions, and may provide an important distortion correction to the direct recombination. The distinct signature of the RDR is the quasi-discrete low energy x-rays emitted during the capture, shifted down in energy by the excitation energies of the core electrons. The analog of the RDR must also take place in the ion-atom collisions, as radiative transfer excitation (XTE). Evaluation of the RDR cross section is difficult because of the correlated nature of the transition operator, but detailed qualitative discussions of the RDR are presented. A crude estimate of the cross section is obtained and compared with the other recombination modes. The radiative Auger effect is roughly an inverse of RDR, and the charge dependence of its cross section is improved, using a correlated vertex.

Numerical Liouville approach: Formulation of third-order nonlinear optical susceptibilities

As a continuation of a previous paper [Phys. Rev. A 50, 2989 (1994)], this article develops and describes in detail the new nonperturbative approach to the third-order nonlinear optical susceptibilities χ(3)g(ω) in third-harmonic generation (THG), electric-field-induced second-harmonic generation (EFISH), degenerate four-wave mixing (DFWM), electric-field-induced optical rectification (EFIOR), and electric-field-induced Kerr effect (EFIKE) for N-state quantum systems interacting with intense electric fields. The present method utilizes the Fourier transformation of numerically exact solutions of the Liouville equation, so that it can provide both real and imaginary nonlinear optical spectra valid for arbitrary laser intensities, frequencies, and relaxation. As an application of the method, we investigate the characteristics of nonlinear optical spectra in THG, EFISH, and DFWM for a three-state model that mimics the electronic excited states of t-octatetraene obtained from a full configuration interaction (FCI) calculation using the Pariser–Parr–Pople (PPP) Hamiltonian. Comparisons between the present nonperturbative and the conventional perturbative results are also carried out. The magnitudes of the third-order nonlinear susceptibilities in the off-resonant region show the following trend: χ(3)(THG)≳χ(3)(EFISH)≳χ(3)(DFWM), with χ(3)(THG) exhibiting the largest frequency dispersion.

Third-order non-linear optical susceptibilities of CdIn 2O 4 thin films

Third-order non-linear optical susceptibilities, χ (3)(−3 ω; ω, ω, ω), for spinel-type oxide thin films prepared by rf magnetron sputtering were evaluated using the third-harmonic generation method in the off-resonant region. The χ (3)(−3 ω; ω, ω, ω) of MgAl 2O 4 was about 1.0 × 10 −12 esu and that of CdIn 2O 4 ranged from 1.8 to 4.5 × 10 −12 esu, which seemed to be relatively large compared with other inorganic materials. The origin of the large χ (3)(−3 ω; ω, ω, ω) was the spinel-type structure (AB 2O 4). Since octahedra with B-site element in the center are linked by sharing an edge in space, it was expected that the delocalization of the s-orbital of the B-site metal would be large. The reason why the χ (3)(−3 ω; ω, ω, ω) of CdIn 2O 4 was several times larger than that of MgAl 2O 4 was that the optical band gap of CdIn 2O 4 was smaller than that of MgAl 2O 4.

Molecular Design of Nonlinear Optical Polymeric Materials for Switching Device Application

Abstract Molecular design of nonlinear optical (NLO) polymeric materials for device application such as ultrafast optical switches are discussed. It is necessary to fabricate channel waveguides to realize polymeric NLO switching devices that can be driven with lower laser power. For that purposes, we have proposed a molecular structure of processable NLO polymers where the reduction of an attenuation loss and the attainments of higher processability of the polymers are achieved. Third-order nonlinear optical properties, χ(3), of novel NLO polymers were around 10−10 esu at 1.5 μm wavelength region. Even in off-resonant regions, their χ(3) values are around 5 × 10−11 esu. Single mode channel waveguides of the polymers are fabricated using a standard photo-process. Attenuation loss through the film and that for the single mode waveguide at 1.32 μm wavelength was also reported.

Molecular Design of Nonlinear Optical Polymers for Photonic Device Applications

ABSTRACTMolecular design of processable nonlinear optical (NLO) polymers is discussed for applications to devices such as ultrafast optical switches. Channel waveguides must be fabricated in order to develop polymeric NLO switching devices that can be driven with lower laser power. For these purposes, we propose molecular structures that reduce attenuation loss and allow the development of highly processable NLO polymers. Third-order nonlinear optical properties, χ(3), of the novel NLO polymers are around 10−10 esu in the 1.5 μm wavelength region. Even in off-resonant regions, the χ(3) values are around 5 × 10−11 esu. Single Mode channel waveguides of the polymers are fabricated using a standard photo-process. Attenuation loss through a film and also for a single mode waveguide at 1.32 μm wavelength is Measured. Nonlinear optical properties of novel, processable, heteroaromatic polymers with large χ(3) are also discussed. Several types of heteroaromatic polymers are developed with a structure in which π-electron excessive heteroaromatic compounds and π-electron deficient heteroaromatic compounds are combined to induce strong nonlinearity. The charge transfer between heteroaromatic rings on the π-conjugated sequences is thought to influence the properties of certain excited states that enhance χ(3) These polymers have excellent potential for use in fabrication of optical switching devices.

Disorder in GeSe 2 small crystals and medium-range structure in amorphous GeSe 2

The Raman scattering spectra of various forms of GeSe 2, such as amorphous films, single crystals, and small crystals prepared by a gas-evaporation deposition technique, are investigated with an excitation photon energy ranging from 2.1 to 2.8 eV. In the spectra of the crystals, there are two Raman bands, originating from two types of breathing vibrations of the GeSe 4 2 tetrahedra: one is spread over the corner-sharing tetrahedra and the other is quasi-localized on the edge-sharing tetrahedra. In addition to the resonant Raman scattering related to the edge-sharing tetrahedra through the exciton transition observed with 2.71 eV excitation in the single crystals, a new resonant spectrum is found only in the small crystals with 2.54 eV excitation. With increasing disorder in the crystals, the intensity ratio between the two breathing vibration bands increases in the off-resonant excitation region. The Raman spectra in the amorphous states are ascribed to the breathing vibrations of GeSe 4 2 tetrahedra which form a medium-range structure topologically similar to that of crystalline fragments.

Albrecht theory of resonance Raman scattering: applied to conjugated polymers in the solid-state limit

The connection between the vibronic picture of Raman scattering and the third-order perturbation approach in solid-state physics is clarified. Starting from the Kramers—Heisenberg—Dirac formula for Raman scattering, we derive analytical expressions for the Condon and Herzberg—Teller terms for polyacetylene in the solid-state limit. Close to resonance the Condon term dominates and converges to the usual solid-state result. In the off-resonance region the Herzberg—Teller term is comparable to the Condon term, in contrast to the small molecule case.

Third-Order Nonlinear Optical Properties of a Series of Systematically Designed Conjugated Rigid-Rod Polyquinolines

ABSTRACTThe third-order nonlinear optical properties of thin films of two series of conjugated rigid-rod polyquinolines, exemplified by poly(2, 2'-(l, 4-phenylene)-6, 6'-bis(4-phenyl quinoline)) (PPPQ, 2d) and poly(2, 7-(l, 4-phenylene)-4, 9-diphenyl-l, 6-anthrazoline) (PPDA, 3d), were investigated by third harmonic generation spectroscopy. Of the nine polyquinolines with diverse backbone structures, PPPQ has the largest optical nonlinearity with a χ(3) (-3ω; ω, ω, ω) value of 3.2 × 10−12 esu and 3.3 × 10−11 esu in the off-resonant and three-photon resonant regions, respectively. A comparison of the nonresonant χ(3) of the series of nine systematically derived polyquinolines showed that a scaling law of the form χ(3) ∼ (λmax)v ∼ Eg-v does not hold; in fact, the nonresonant χ(3) was essentially independent of the optical bandgap. These results suggest that structure-χ(3) propeny relationships in polymers cannot be inferred from those of oligomers and model compounds.

Scattering of electromagnetic fields of any state of coherence from space-time fluctuations.

A theory is developed, valid within the accuracy of the first-order Born approximation, of the scattering of electromagnetic fields that applies under much more general conditions than do the current theories. The incident field is assumed to be statistically homogeneous and stationary, of arbitrary state of coherence, of arbitrary state of polarization, and to have arbitrary spectrum. The medium is assumed to be linear and spatially and temporally random, with the randomness being characterized by an ensemble that is statistically homogeneous, isotropic, and stationary. The analysis is not restricted to scattering from a medium in thermal equilibrium and applies in both off-resonance and near-resonance regions of the medium.

Neutron total cross-section measurement of 232Th in the off-resonance region below 300eV

The neutron total cross section of 232Th at the off-resonance energies from thermal neutron to 300 eV has been measured by the linac time-of-flight method. Neutrons transmitted through a Th sample were detected with a 6Li glass scintillator, 12.7 cm in diameter and 1.27 cm thick, placed at the 22 m station. Below 20 eV, the present result is in good agreement with the recent measurements at RPI, ORNL and BNL, and is close to BNL's data in the higher energy region. The evaluated nuclear data of ENDF/B-IV are distinctly lower in the energy region from thermal neutron to 300 eV than the present values. The JENDL-2 data are, however, close to the present result.

Differential electron spin polarisation effects in the two-photon ionisation of atomic caesium

The two-photon ionisation of atomic caesium from the ground state irradiated with monochromatic circularly polarised radiation is analyzed theoretically in the framework of spin-orbit coupling, which leads to the existence of a differential spin polarisation of the ejected electrons in the z direction. This may give important information about the intermediate resonances and also for the off-resonant region where multiphoton ionisation takes place through intermediate virtual transitions. The essential features of differential spin polarisation are studied and the analysis of the results leads to the suggestion that it should be possible to obtain highly polarised electrons according to the properties of the incident radiation used.