Neutron diffraction and inelastic scattering from adsorbed molecules

Neutron scattering measurements on the structure and dynamics of adsorbed phases at the gas solid interface have proliferated in the last five years and this paper reports some recently obtained results for the systems methane-graphite and ammonia-graphite, which show BET type I and type III isotherms respectively. These systems clearly illustrate the differences in both structure and dynamics to be expected in other examples where either wetting of the surface or non-wetting behaviour occurs upon adsorption. Evidence for phase transitions in both types of system coming from diffraction is reported, and this is substantiated by measurements using inelastic scattering to follow the molecular dynamics. The neutron inelastic scattering from molecules adsorbed on platinum black and in zeolites reveals some of the virtues of neutron inelastic scattering for the study of chemisorbed species. Finally, some preliminary experiments on neutron small angle scattering at the solid liquid interface in polystyrene latex-water sols are reported.     

Many-body field theoretic framework for inelastic pion-nucleus scattering

We consider inelastic scattering of pions from nuclei using many-body quantum field theory methods. We find that, in an inelastic amplitude for small energy transfer, one can separate out effects of particle-hole correlations in the final nuclear state. The ratio of π⁺ and π^? inelastic cross sections can differ substantially from the analogous ratio for free πN scattering.     

Neutron inelastic scattering to octupole states in single-closed-shell nuclei

Differential cross sections for the excitation of the first octupole-vibrational state in the closed- neutron-shell nuclides ⁸⁸Sr and ⁹⁰Zr and in the closed-proton shell-nuclei ^{116, 118, 120, 124}Sn by 11 MeV neutrons are presented. The distorted-wave Born approximation is used to obtain deformation lengths, σ(3^?), for each state. Results are compared with earlier measurements of inelastic proton scattering to the same states. Although limited resolution in the neutron time- of-flight spectrometer complicates the interpretation of the Sn data, the overall conclusion that σ_nn′(3^?) ≈ σ_pp′(3^?) is supported by all of the measurements.     

Neutron inelastic scattering from 40Ca at 21.7 and 25.5 MeV

Differential cross sections for the scattering of neutrons from ⁴⁰Ca for states up to 5 MeV excitation energy have been measured at 21.7 and 25.5 MeV. The analysis is done using a coupled channel formalism in terms of a vibration collective model. The results using a usual standard Woods-Saxon form factor for the transitions are compared with those obtained using form factors derived from a model-independent analysis to the elastic cross sections.     

Pressure-induced valence anomaly in TmTe probed by resonant inelastic X-ray scattering

The pressure-induced valence transition in TmTe was investigated by resonant inelastic x-ray scattering at the Tm L3 edge, a powerful probe of the rare-earth valent state. The data are analyzed within the Anderson impurity model which yields key parameters such as the Tm 4f-5d hybridization. In addition to the general tendency of the f electrons towards delocalization, we find a plateau in both the Tm valence and hybridization pressure dependences between 4.3 and 6.5 GPa which is interpreted in terms of an n-channel Kondo (NCK) screening process. This behavior is at odds with the usually continuous, single-channel Kondo-like f delocalization while being supported by the seminal calculations of the NCK temperature in Tm ion by Saso et al. Our study raises the interesting possibility that an NCK effect realized in a compressed mixed-valent f system could impede the concomitant electron delocalization.     

Crystal field spectroscopy by inelastic neutron scattering

We present a review of inelastic neutron scattering results on very diluted rare earth (RE)-Laves phases. A systematic investigation to study crystal electric fields, experienced by single rare earth ions in a metallic environment, was done on (RE,R)Al₂, with RE=Pr, Nd, Tb, Dy, Ho, Er, Tm andR=Sc, Y, La. We show the influence of the 4f-ions on the crystal fields as well as the influence of the host lattices. The rare earth atoms in ScAl₂ have been studied for the first time and most of the other alloys, with LaAl₂ and YAl₂ as hosts, have been studied for the first time with magnetic atom concentrations below 1 at% and/or with good resolution for low energy excitations. Furthermore we studied the dynamics of 4f-moments, which are coupled to the conduction electrons by determining the coupling constants. We present a comprehensive set of crystal field parameters and coupling constants from these systematic studies and discuss them qualitatively within the available theoretical models. The influence of magnetic atom concentration on crystal field spectra will be shown in part II.     

Neutron scattering in a Leibfried-Brenig spectrum space lattice

The classical high-temperature limit of the pair self-correlation function for a system of harmonic oscillators as introduced by Sunakawaet al. is applied to a lattice whose vibrational spectrum is described by a Leibfried-Brenig approximation. The resulting neutron scattering cross-section is discussed qualitatively; it is shown that the principle of detailed balance is fulfilled.     

Theory of resonant inelastic X-ray scattering spectrum for Ni impurities in cuprates

We perform the numerically exact diagonalization calculation for small Cu-O clusters with a Ni impurity site, representing the Ni-substituted cuprate, to examine the single-particle excitation spectra as well as the resonant inelastic X-ray scattering (RIXS) spectra. We clarify relations between low-energy electronic structures near the Ni site and excitations seen in the RIXS spectra.     

Multiphonon atom-surface scattering from corrugated surfaces: derivation of the inelastic scattering spectrum for diffraction states

A strictly quantum mechanical derivation of the energy and parallel momentum resolved scattering spectrum formula that combines the effects of the diffraction of atoms from corrugated surfaces and multiple inelastic scattering by dispersive phonons is presented. The final result is expressed in the compact and numerically tractable form of a Fourier transform of a cumulant expansion in which each term embodies an interplay between the processes of projectile diffraction and multiphonon scattering to all orders in the respective interaction potentials. The Debye-Waller reduction of the intensities of diffraction peaks is explicitly formulated.     

Neutron elastic and inelastic scattering from 28Si, 32S and 34S

Differential cross sections for the elastic and inelastic scattering of neutrons from the sd-shell nuclei ²⁸Si, ³²S and ³⁴S have been measured in the 20–26 MeV region. The data are analyzed in terms of the rotation-vibration (²⁸Si) and anharmonic vibration (^{32, 34}S) collective models. Isoscalar E2, E3 and E4 transition matrix elements are obtained from the normalized multipole moments of the real potential and the results are compared with those obtained from electromagnetic probes and from nuclear structure theoretical calculations.     

Thermomechanical properties of graphene: valence force field model approach

Using the valence force field model of Perebeinos and Tersoff (2009 Phys. Rev. B 79 241409(R)), different energy modes of suspended graphene subjected to tensile or compressive strain are studied. By carrying out Monte Carlo simulations it is found that: (i) only for small strains (|ε| 相似文献   

Folding-model analysis of elastic and inelastic α-particle scattering using a density-dependent force

A folding model with a density-dependent form of the semi-realistic M3Y effective interaction is applied to α-particle scattering. A previous analysis of elastic scattering at 140 and 172 MeV is now applied to data at other energies from 25 to 120 MeV. The model is also extended to inelastic scattering, using both the collective model and a valence-plus-core-polarization model for the transition densities. The proton transition densities were normalized to measured B(EL) values. When necessary, the neutron transition densities were rescaled to fit the (α, α′) data, providing a source of information on the neutron contributions. The neutron transition multipole moments thus obtained are compared to those derived from (p, p′) data at 800 MeV, as well as from other sources.     

Neutron total,scattering and inelastic Gamma-ray cross sections of yttrium at few MeV energies

Neutron total, scattering and (n; n′,γ) cross sections of elemental yttrium (⁸⁹Y) were measured in the few-MeV region. The neutron total-cross-section measurements were made with broad resolutions from ≈0.5 to 4.2MeV in steps of ?0.1 MeV. Neutron elastic- and inelastic-scattering cross sections were measured from ≈1.5 to 4.0 MeV, at incident-neutron energy intervals of ≈50keV and at ten or more scattering angles distributed between 20 and 160 degrees using neutron detection. Inelastic-scattering cross sections were also determined using the (n; n′,γ) reaction at incident energies from 1.6 to 3.8 MeV at intervals of 0.1 MeV. Gamma-rays and/or inelastically-scattered neutrons were observed corresponding to the excitation of levels at: 909.0±0.5, 1,507.4 ±0.3, 1,744.5±0.3, 2,222.6±0.5, 2,530±0.8, 2,566.4±1.0, 2,622.5±1.0, 2,871.9 ±1.5, 2,880.6±2.0, 3,067.0±2.0, 3,107.0±2.0, 3,140.0±2.0, 3,410.0±2.0, 3,450.0±2.0, 3,504.0 ±1.5, 3,514.0±2.0, 3,556.0±2.0, 3,619.0±3.0, 3,629.0±3.0 and 3,715.0±3.0 keV. The experimental results are discussed in terms of the spherical-optical-statistical, coupledchannels, and core-coupling models, and in the context of previously reported excitedlevel structure.     

Fermi-particle scattering at a central force field

In this article, we study the scattering of free electrons and neutrons of an arbitrary force center having a charge and magnetic moment, taking into account the electric and magnetic anomalous moments of the Fermi particle. Polarization effects of scattering are also considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 97–101, December, 1976.     

Path integral methods for inelastic scattering

Corrections to the primitive semi-classical amplitude for multiple inelastic scattering are obtained from a path integral formulation of scattering theory. The path integrals are calculated by making an expansion about a classical orbit describing elastic scattering. Terms are collected to give a series in inverse powers of the reduced mass m of relative motion of the target and projectile. The leading term is the primitive semi-classical amplitude for multiple excitation and explicit formulae are given for the corrections of order $\text{1}\text{m}$. These are calculated in detail for a one-dimensional model. It is shown that some, but not all, of the corrections can be included by evaluating the primitive amplitude with a symmetrized orbit.     

Unitarity relation for deep inelastic scattering

Saturating the multiparticle states in the unitarity relation for virtual Compton scattering by two-particle states consisting of an infinite set of high mass vector mesons and a nucleon leads to a non-linear integral equation the solution of which determines the behaviour in the scaling limit and the non-forward scaling functions for deep inelastic scattering.