Electron–Phonon Renormalization of the Electron Mass in a Metal beyond the Adiabatic Approximation

Journal of Experimental and Theoretical Physics - We analyze the renormalization of the electron mass due to the electron–phonon interaction and interaction constant λ associated with...     

A quantitative assessment of the three-dimensional microstructure of a γ-γ ′ alloy

We present the first quantitative analysis of the three-dimensional microstructure of a n- n' alloy that does not make any a priori assumptions about the n'-particle morphologies. The n'-particle size distribution is derived using the particle volumes to provide a measure of the particle sizes that is independent of particle morphology and is found to be somewhat broader and to have a lower maximum peak height than the theoretical prediction in the absence of elastic stress. Non-equiaxed n' particles are found to be approximately equally likely to have rod-like, plate-like or mixed-character morphologies. In contrast with theoretical predictions, smaller particles tend to be more non-equiaxed than larger particles. The latter two findings are a result of the attractive interparticle configurational forces induced by stress at the corners of neighbouring particles. By analysing the distribution of particle side lengths, it is concluded that the average thickness of the sheets of n'-particles is between 0.4 and 0.6 µm.     

Electron spin resonance spectrum for a radical in γ-irradiated N-iodosuccinimide

A radical exhibiting a very large hyperfine coupling to ¹²⁷I, together with a small coupling to ¹⁴N, formed in γ-irradiated N-iodosuccinimide at 77 K is identified as a σ* radical anion in which the added electron is accommodated primarily in the N-I antibonding σ-orbital.     

Analysing Imaging Signals of Negative－Charging Contrast in Scanning Electron Microscopy ＊

Negative charging of a specimen may produce the image contrast of yielding the information under the in-sulating thin film in scanning electron microscopy. To clarify and make good use of the recently developednegative-charging contrast (NCC), we propose a simplified procedure for quantifying secondary electron (SE)imaging signals and report the calculated results. The theoretical considerations and calculations are validatedby comparing the calculated relation between the SE signal and the surface potential with measured dynamiccharacteristics of the NCC images. The results show that in the region of weak negative charging the NCCformation is due to the SE redistribution. The intensity of SE signals decreases with increasing the amount ofthe SEs returning to the negatively charged surface whose local electric field may attract electrons. This resultsin the NCC transient characteristics.     

Rigidity of Interfaces in the Falicov–Kimball Model

We analyze the thermodynamic properties of interfaces in the three-dimensional Falicov–Kimball model, which can be viewed as a primitive quantum lattice model of crystalline matter. In the strong coupling limit, the ionic subsystem of this model is governed by the Hamiltonian of an effective classical spin model whose leading part is the Ising Hamiltonian. We prove that the 100 interface in this model, at half-filling, is rigid, as in the three-dimensional Ising model. However, despite the above similarities with the Ising model, the thermodynamic properties of its 111 interface are very different. We prove that even though this interface is expected to be unstable for the Ising model, it is stable for the Falicov–Kimball model at sufficiently low temperatures. This rigidity results from a phenomenon of ground-state selection and is a consequence of the Fermi statistics of the electrons in the model.     

A Novel Contactless Method for Characterization of Semiconductors：Surface Electron Bean Induced Voltage in Scanning Electron Microscopy

We present a novel contactless and nondestructive method called the surface electron beam induced voltage (SEBIV) method for characterizing semiconductor materials and devices.The SEBIV method is based on the detection of the surface potential induced by electron beams of scanning electron microscopy (SEM).The core part of the SEBIV detection set-up is a circular metal detector placed above the sample surface.The capacitance between the circular detector and whole surface of the sample is estimated to be about 0.64pf.It is large enough for the detection of the induced surface potential.The irradiation mode of electron beam (e-beam) influences the signal generation When the e-beam irradiates on the surface of semiconductors continuously,a differential signal is obtained.The real distribution of surface potentials can be obtained when a pulsed e-beam with a fixed frequency is used for irradiation and a lock-in amplifier is employed for detection.The polarity of induced potential depends on the structure of potential barriers and surface states of samples.The contrast of SEBIV images in SEM changes with irradiation time and e-beam intensity.     

Nanoscale Studies of the Chemistry of a René N6 Superalloy

Atom-probe field-ion microscopy (APFIM) is used to study partitioning of the alloying elements between the (FCC) and (L1₂) phases and their segregation behavior at / interfaces of a René N6 nickel-based superalloy. The atomic-scale resolution and real space reconstruction capability for elemental chemical mapping makes three-dimensional atom-probe microscopy especially suitable for subnanoscale investigations of complex multicomponent superalloys. Concentration profiles of this alloy, obtained from an atom probe analysis, reveal the partitioning behavior of the alloying elements in René N6. As anticipated, the matrix strengtheners, such as Mo and W, are partitioned to the (FCC) matrix, while Re segregates at the / interfaces; the Gibbsian interfacial excess of Re is determined by both one-dimensional (2.32 atoms nm^–2) and three-dimensional atom-probe microscopies (3.92 atoms nm^–2) and the values obtained are in reasonable agreement.     

Electron spin resonance identification of phosphorus-centred radicals in γ-irradiated dialkyl phosphites

Potential curves have been calculated by the ab initio MRD CI method for states of OH⁺ correlating with O(³ P, ¹ D, ¹ S) + H⁺ and O⁺(⁴ S, ² D, ² P) + H. Spectroscopic constants derived from the calculated potential curves are in good agreement with the available experimental data. The calculations support the experimental assignment of vibrational quantum numbers for levels perturbing the A ³Π state.     

Harmonics in a Quantum Free Electron Laser: Towards a compact, coherent γ-ray source

Short-wavelength Free Electron Lasers (FELs), which have recently produced intense, hard X-rays are currently based on the concept of classical Self-Amplified Spontaneous Emission (SASE). In order to extend the production of intense, coherent radiation to sub-Å wavelengths then an alternative to the conventional SASE-FEL concept will be necessary, as conventional SASE-FELs require long wigglers (~ 100 m) and large accelerators (~ km) and produce radiation which has poor temporal coherence. Recently, we have introduced the concept of the Quantum Free Electron Laser (QFEL). The QFEL is characterised by quantised electron momentum recoil and the emission of monochromatic, coherent radiation from a compact apparatus. This makes it appealing for applications requiring a high degree of temporal coherence. We show that a SASE-QFEL may offer the possibility to produce intense, coherent γ-rays via harmonic generation. This has the potential to open up new applications e.g. coherent interactions involving nuclear transitions.     

Effect of Multiple Scattering of a Relativistic Electron Beam in a Gas–Plasma Medium on the Dynamics of the Resistive Hose Instability

We consider the effect of the multiple Coulomb scattering on the spatial dynamics of the relativistic hose instability of a relativistic electron beam propagating along an Ohmic plasma channel. It is shown that the enhancement of scattering noticeably suppresses this instability.

     

Electron Correlation in the Final Continuum of Ionization Hydrogen by 150-eV Electron Impact

Electron correlation in triple differential cross sections for ionization of atomic hydrogen by electron impact is analysed for the case of coplanar asymmetric geometry within the framework of the two-potential formulae. Based on the approximations of projectile and faster-electron plane wave, the transition matrix element is analytically expressed to be a product of two factors: the correlation factor of two electrons in the final channel and the structure-scattering factor. The contribution of both the factors to the angular distribution of the triple differential cross section is calculated. The present results are compared with the experimental data and the other theoretical calculations for the incident energy of 150eV.     

On the Spin Depolarization of a Hall Ferromagnet in the Vicinity of ν = 1 in Two-Dimensional Electron Systems Based on ZnO

JETP Letters - The behavior of the degree of spin polarization and the specific exchange energy near the Hall ferromagnetic state with filling factor ν = 1 in strongly interacting...     

Energy calibration of a BC501A liquid scintillator using a γ-γ coincidence technique

An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.     

Energy calibration of a BC501A liquid scintillator using a γ-γ coincidence technique

An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.     

Insitu Plane—View and Cross—Scctional Transmission Electron Microscopy of Fractal Formation in Au／a—Ge Bilayer Films

Fractal crystallization in Au/a-Ge bilayer films has been studied by in situ plane-view and cross-sectional transmission electron microscopy.The experimental evidence suggests that the fractal crystallizaqtion is controlled by both diffusion and reaction processes.The growth kinetics analysis indicates that both diffusion-limited aggregation and random successive nucleation mechanisms play an important role in fractal crystallization in Au/a-Ge bilayer films.     

Shearing of γ′ precipitates in Ni-base superalloys: a phase field study incorporating the effective γ-surface

An extended phase field model of dislocations in Ni-base superalloys is presented. It incorporates the recently developed effective γ-surfaces for both matrix and precipitate phases, obtained from atomistic simulations. These novel γ-surfaces feature extrinsic stacking faults as additional local minima. Thus, they offer an increased number of available dislocation dissociation pathways within the phase field system. The new model has been used to simulate a variety of mechanisms for γ′ precipitate shearing proposed in literature. A critical assessment is made based on the modelling observations.     

Predicting the onset of rafting of γ′ precipitates by channel deformation in a Ni superalloy

The growth or shrinkage, normal to {001}, of the interfaces between the γ matrix and cuboidal γ′ precipitates is examined for a Ni-base superalloy, by considering the force acting on the interfaces. The force is produced by the precipitate coherency misfit and the stress produced by plastic deformation in channels of the γ matrix. A simple expression, which directly addresses the origin of the surface force, is given. The plastic deformation within the initially active γ matrix channels exerts the force to cause rafting. The subsequent activation of other types of channels also promotes the rafting in the same direction as the first active channels, when the plastic strain of the former channels increases. These issues are also discussed in terms of analysis based on those dislocations caused by the precipitate misfit and those produced by the plastic deformation.