Two-step processes in inelastic proton scattering

A discussion is given of effects ofp-d-p′ type two-step processes on inelastic scattering from¹⁶O and⁴⁰Ca with incident proton energies between E_p=25 and 46 MeV. It is found that the two-step processes increase the magnitude of the cross-section by about 20 % without altering the shape significantly.     

Many-photon effects in inelastic light scattering

The usual approach to second harmonic generation (SHG) is based on low-order pertubation theory and neglects the changes in the electronic states that are induced by the exciting beam. To see whathappens in this approximation fails we propose a new formalism, based on the method of excitation amplitudes, to set up a theory of the SHG response and other inelastic light scattering phenomena. We develop the quantum theory in the dipole approximation and show that the inclusion of electron-photon coupling to all others leads to new features. Strong exciting fields produce a nonnegligible SHG response in highly polarisable centro-symmetric systems, and the emitted spectrum shows a dynamical Stark effect.     

Low-frequency inelastic light scattering from As-S glasses

Raman scattering from As-S glasses were observed in the low-frequency region, from 5 to 60 cm^?1. The spectral features depend on the quenching and annealing conditions as well as on the temperature and the composition. The spectrum was explained in terms of the vibration of the layer-like clusters coupled with each other through van der Waals forces.     

Deep inelastic electron scattering on light nuclei

Czechoslovak Journal of Physics -     

Multi-step processes in high-energy elastic and inelastic nuclear scattering

Multi-step processes in elastic and inelastic nuclear scattering at intermediate and high energies are investigated using a formulation whereby a finite number of channels are explicitly treated while all the other channels are approximately accounted for through a “second-order potential matrix”. Within the framework of the eikonal approximation the problem reduces to a finite system of first-order coupled integro-differential equations with non-local potentials which depend on the two-body density matrix of the target nucleus. The relationship of the above formulation to the DWIA, the close-coupling method, and the Glauber multiple scattering model is examined. This approach is applied to the elastic and inelastic (2⁺, 4.43 MeV) scattering of 1 GeV nucleons by ¹²C. The corrections to the DWIA are sizeable, and the inelastic scattering appears to be very sensitive to the multi-step contributions and the nuclear structure.     

Resonant enhancement of inelastic light scattering in strongly correlated materials

We use dynamical mean field theory to find an exact solution for inelastic light scattering in strongly correlated materials such as those near a quantum-critical metal-insulator transition. We evaluate the results for q=0 (Raman) scattering and find that resonant effects can be quite large, and yield a double resonance, a significant enhancement of nonresonant scattering peaks, a joint resonance of both peaks when the incident photon frequency is on the order of U, and the appearance of an isosbestic point in all symmetry channels for an intermediate range of incident photon frequencies.     

Resonant inelastic X-ray scattering of tantalum double perovskite structures

In this paper, we investigated the electronic structures and defect states of SrLaMgTaO₆ (SLMTO) double perovskite structures by using resonant inelastic x-ray scattering. Recently, Eu³⁺ doped SLMTO red phosphors have been vigorously investigated due to their higher red emission efficiency compared to commercial white light emitting diodes (W-LED). However, a comprehensive understanding on the electronic structures and defect states of host SLMTO compounds, which are specifically related to the W-LED and photoluminescence (PL), is far from complete. Here, we found that the PL spectra of SLMTO powder compounds sintered at a higher temperature, 1400 °C, were weaker in the blue emission regions (at around 400 nm) and became enhanced in near infrared (NIR) regions compared to those sintered at 1200 °C. To elucidate the difference of the PL spectra, we performed resonant inelastic x-ray spectroscopy (RIXS) at Ta L-edge. Our RIXS result implies that the microscopic origin of different PL spectra is not relevant to the Ta-related defects and oxygen vacancies.     

Collective processes during stimulated light scattering

An approach to the analysis of the phase conjugation by stimulated light scattering that is alternative to the mode theory of 3D hologram, which is usually applied for these purposes, has been studied. As is known, the use of the mode theory is based on the phenomenological gain factor of the Stokes wave, which is induced by a pump wave in a nonlinear medium. The approach developed in this work directly considers the interaction between plane components of the pump and Stokes waves via hypersonic gratings of the dielectric permittivity, which the pump and Stokes waves induce in the medium. It has been shown that, as a result of the phase conjugation, two hypersonic gratings participate equally efficiently in the interaction between any pair of plane components of the pump and Stokes waves, with one of these gratings being excited by the interacting waves themselves. The other grating in each such pair is unambiguously identified with a simplest vector diagram. Conditions have been analyzed under which numerous other gratings, which could also participate in the interaction of each pair of plane components of the pump and Stokes waves without violating the Bragg conditions and the joining conditions of the transverse components of the wave vectors at the interface between the two media, contribute negligibly to stimulated light scattering. It has been shown that, if the pump is spatially coherent, the considered approach yields the same results as the standard mode theory does. In October 2011, I reported the results of this work at the Vavilov State Optical Institute at the Memorial Meeting “Half a Century of New Optics in Russia: Lasers, Nonlinear Optics, and Optical Holography” and at the International Conference “Laser Optics—2012” (June 2012).     

Rigorous results concerning light cone dominance in deep inelastic lepton-hadron scattering

We consider a class of distributions, appearing in electro-production and satisfying a Jost-Lehmann-Dyson representation. We then prove without further assumptions that only their singularity structure near the light cone is relevant for the behaviour of their Fourier transform in the Bjorken limit. Furthermore we study the ambiguity in this singularity structure introduced by the fact, that scaling is known only in the space like region of momentum space.Work supported by the Bundesministerium für Forschung und Technologie.     

Resonant mechanisms of inelastic light scattering by low-dimensional electron gases

The contribution of elementary excitations in low-dimensional electron gases to resonant inelastic light scattering is found to be determined by interband transitions involving states at specific wave vectors. In modulation-doped GaAs/GaAlAs quantum wells, we detect only the single-particle excitations (SPE) at resonances with electron-hole transitions at the Fermi wave vector, and only plasmons at resonances with zone-center excitons. The plasmon cross section is comparable to the SPE when double electronic resonance is achieved by tuning the plasmon energy to a valence subband separation.     

Elastic and inelastic scattering of electrons by aligned light nuclei

The contribution to the elastic and inelastic scattering cross sections, , due to alignment of nuclei having axial symmetry was calculated for scattering of unpolarized, ultra-relativistic electrons by⁷Li atoms. This contribution turned out to be on the order of magnitude of the cross section ₀ previously calculated in the absence of nuclear alignment. For various nuclear orientations, the ratios /_o were calculated as a function of the momentum transfer q, which may be useful, for example, in increasing the reliability of identification of quantum numbers of nuclear states and multipole transitions.In contrast with the expression for _o, the expression for contains cross products of reduced matrix elements (RME), along with the squares of their moduli. This permits one, having previously experimentally found ₀ and under various kinematical conditions but for fixed q (the RME depend only on q), to obtain a system of equations for the RME and the statistical tensor g₂, which characterizes the degree of alignment of the nuclear target, along with the separation of the parallel and perpendicular cross sections as in the case of unaligned nuclei. Having solved the system of equations, one finds g₂ both in terms of the moduli of the RME of each multipole transition individually, and also in terms of their relative phases. The additional information thus obtained for each nuclear transition may serve as a more strict criterion for checking models of nuclei used in calculations than measurement of ₀ alone.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 94–98, January, 1990.     

Resonant structures in24Mg+28Si elastic and inelastic scattering

The data on the excitation functions of²⁴Mg+²⁸Si elastic and inelastic (2⁺ ?0⁺, 2⁺ ?2⁺, 4⁺ ?0⁺ and 4⁺ ?2⁺) scattering fromE _c.m.=48.97 to 57.21 MeV have been subjected to a statistical analysis consisting of the calculations of deviation function, cross-correlation function, summed excitation function, cross-channel correlation coefficients, coherence widths, and the distribution of cross sections. Based on the outcome of the analysis resonant structures atE _c.m.=49.23, 50.02, 50.51, 52.10, 52.53, 53.27 and 54.14 MeV have been confirmed and three new structures of the same nature have been identified atE _c.m.=51.42, 54.88 and 55.60 MeV.     

Nonlocal light-cone expansion and its applications to deep inelastic scattering processes

Light-cone dominated scattering processes are studied within the framework of the nonlocal operator product expansion. An integral representation for the Fourier transform of matrix elements of the renormalized product of two currents in the Bjorken region of the momentum space is derived and shown to be convergent everywhere. Renormalization group equations (RGE) for the coefficient functions pertinent to the forward scattering are discussed. It is demonstrated how the evolution equation for the forward amplitude and/or its absorptive part immediately follow (in theleading order) from such RGE. Anomalous dimensions of all relevant nonlocal operators in QCD are calculated in the one-loop approximation and shown to be simply related to the Altarelli-Parisi probability functions.     

Resonant stokes and anti-stokes Raman scattering of light in CdSe/ZnSe nanostructures

Raman scattering spectra of CdSe/ZnSe multilayer nanostructures with a CdSe insert of a nominal thickness of 2.1 monolayers were studied. A heavy dependence of the intensity and of the frequency position of the multiphonon Stokes and anti-Stokes LO bands on the exciting photon energy was detected. The results obtained are interpreted as a resonance with various exciton transitions in the CdSe insert and barrier ZnSe layers. A difference between the Stokes and anti-Stokes frequencies of LO bands observed as the resonance conditions are varied confirms the inhomogeneous nature of the photoluminescence band of CdSe quantum dots.     

Nuclear inelastic scattering

Nuclear inelastic scattering is a new technique to study lattice dynamics. It gives direct access to the density of phonon states. The instrumentation and data analysis are outlined and illustrated by some distinct examples, such as α-Fe, β-Sn, and FeBO₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nuclear inelastic scattering

The development of the new field of nuclear inelastic scattering is reviewed. The experimental technique and the variety of applications are illustrated by recent results obtained at the Nuclear Resonance beamline of the European Synchrotron Radiation Facility. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coherent inelastic light scattering from a microwave-excited array of magnetic particles

Inelastic light scattering from an array of Permalloy particles driven by a microwave magnetic field is shown to be a coherent phenomenon in which the scattered radiation is observed only at diffraction angles corresponding to the reciprocal lattice of the array. The results are explained in terms of the phase coherence of the inelastically scattered light by each of the particles.