Differential inverse inelastic mean free path determination on the base of X-ray photoelectron emission spectra

The photoelectron spectroscopy model is based on the solution of the radiative transfer equation with inner sources. The exact numerical solutions using BDF method are presented. PES, XAES and EELS spectra are described as series by the number of inelastic scatterings. Differential inverse inelastic mean free path for Be and W are obtained from the experimental data by the fitting procedure.     

Size-selective extended X-ray absorption fine structure spectroscopy of free selenium clusters

In a recent paper [M. Yao et al., J. Synchrotron Radiat. 8, 542 (2001)]], we proposed a new method for the size-selective EXAFS (extended x-ray absorption fine structure) of neutral-free clusters, in which not only the x-ray absorption process but also the deexcitation processes are utilized as the structural information. In order to verify this method experimentally, we have developed the synchronous measurements of EXAFS and photoelectron photoion coincidence and carried them out for a Se cluster beam by utilizing the third-generation intense x-ray source. The EXAFS spectra for Se small clusters have been obtained and compared critically with theoretical predictions.     

Transport mean free path for magneto-transverse light diffusion: an alternative approach

Abstract

This paper presents a derivation of the transport mean free path for magneto-transverse light diffusion, ?*_⊥, in an arbitrary random mixture of Faraday-active and non-Faraday-active Mie scatterers. This derivation is based on the standard radiative transfer equation. The expression of the transport mean free path obtained previously from the Bethe–Salpeter equation, for the case where only Faraday-active scatterers are present, is recovered. This simpler formulation can include the case of homogeneous mixtures of Faraday-active and non-Faraday-active scatterers.     

Transport mean free path for magneto-transverse light diffusion: an alternative approach

This paper presents a derivation of the transport mean free path for magneto-transverse light diffusion, ℓ*_⊥, in an arbitrary random mixture of Faraday-active and non-Faraday-active Mie scatterers. This derivation is based on the standard radiative transfer equation. The expression of the transport mean free path obtained previously from the Bethe-Salpeter equation, for the case where only Faraday-active scatterers are present, is recovered. This simpler formulation can include the case of homogeneous mixtures of Faraday-active and non-Faraday-active scatterers.     

Subshell photoionization cross-sections,electron mean free paths and quantitative X-ray photoelectron spectroscopy

Subshell photoionization cross-sections (SPC) for elements of atomic number in the range 3?, z ? 82 have been determined from measurement of relative photoelectron intensities at a photon energy of 1486.6 eV (Al Kα). A correction procedure has been developed which permits such determinations even when sample surfaces are not atomically clean. The results obtained suggest that Scofield's SPC calculations [2] are reasonably reliable for 1s, 2p and 3d subshells but that the present, experimentally derived data are to be preferred for quantitative use. As a result of this work, a rapid method of quantitative surface-constituent analysis, accurate to ± 20%, has also been developed, which is expected to be of value particularly in industrial situations. A semi-empirical method of extracting electron mean free paths from measurements of relative photoelectron intensities is also illustrated.     

A nuclear matter approach to the mean free path of a nucleon in a system of colliding ions

We calculate the mean free path of the projectile nucleons in an ion-ion system. The lab. bombarding energies correspond to 70 MeV/A to 220 MeV/A above the Coulomb barrier. The effect due to the Pauli blocking is studied.     

Pion mean free path in nuclear matter

The mean free paths for true absorption and inelastic scattering-as well as true absorption alone-of pions in symmetric nuclear matter are deduced from two sets of optical model parameters.     

Nucleon mean free path in nuclear matter

In calculations of nuclear reaction yields at incident energies of some tens of MeV consistently better agreement with experiments is obtained by assuming a nucleon mean free path in nuclear matter longer than that deduced from the Fermi gas model and free nucleon-nucleon cross sections.     

用概率知识推导Tait平均自由程

通过一些简单的概率假设，给出了Tait平均自由程的新的推导，并讨论了对强度分布的影响。     

Attenuation mean free path of hadrons in super-families

Summary Results are presented from the collaboration work of groups of Moscow State University and Waseda University with Pamir X-ray film chamber of thick Pb type. Hadrons in 58 families with energy >100 TeV are studied. The attenuation m.f.p. is 233±40 g/cm² in Pb. Paper presented at the Special Session on very high-energy cosmic-ray interactions (super-families) of the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Self-consistent Green's function calculation of the nucleon mean free path

The extension of Green's functions techniques to the complex energy plane provides access to fully dressed quasiparticle properties from a microscopic perspective. Using self-consistent ladder self-energies, we find both spectra and lifetimes of such quasiparticles in nuclear matter. With a consistent choice of the group velocity, the nucleon mean-free path can be computed. Our results indicate that, for energies above 50?MeV at densities close to saturation, a nucleon has a mean-free path of 4 to 5?fm.     

Thermal conductivity spectroscopy technique to measure phonon mean free paths

Size effects in heat conduction, which occur when phonon mean free paths (MFPs) are comparable to characteristic lengths, are being extensively explored in many nanoscale systems for energy applications. Knowledge of MFPs is essential to understanding size effects, yet MFPs are largely unknown for most materials. Here, we introduce the first experimental technique which can measure MFP distributions over a wide range of length scales and materials. Using this technique, we measure the MFP distribution of silicon for the first time and obtain good agreement with first-principles calculations.     

Photoacoustic X-ray absorption fine-structure spectroscopy of the NiK-edge

The X-ray absorption in a 5 m thick Ni foil for energies from 8.2 keV to 8.8 keV was measured by the photoacoustic method using a gas-microphone-cell. Results are presented for both photoacoustic amplitude and phase as a function of incident photon energy. The absorption fine structure above the NiK-edge is clearly resolved. The data are compared with a simple theory for the signal generation, and discrepancies are explained by discussing the various energy dissipation channels following the X-ray absorption.     

X-ray absorption spectroscopy and high pressure

Abstract

The difficulties of the adaptation of high pressure to x-ray absorption are presented. The advantages of the energy-dispersive geometry are discussed as well as the future improvements expected with the new synchrotron radiation sources.

Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’, Daresbury Laboratory 20-21 July 1991     

Measurement of the electron mean free path using a bending effect

It has been observed experimentally that elastically bending a metal whisker increases its resistance. Such an increase in resistance depends on the metal, the temperature and the orientation of the whisker axis. This effect is observable below 6°K for Zn, 8°K for In, 20°K for Sn, and 300°K for Bi. It is suggested that the effect may be due to an enhancement of surface scattering due to the bending of the whisker. A calculation for such an effect for an “ideal metal” is presented along with data for Zn and Bi. This work has been supported by the Air Force Office of Scientific Research under grant number 68-1548.     

Spatial variation of the electron mean free path near a surface

The electron plasmon-emission-mean-free-path in semi-infinite Jellium is evaluated as a function of position, and of electron emergence angle. The usual assumption that this free path is spatially non-varying inside the “metal” is found to be a reasonable approimation to reality by virtue of the fact that the surface plasmon emission probability increases where that of the bulk plasmon decreases (and vice-versa). The inverse mean free path, however, does not fall to zero for an appreciable distance (on the order of angstroms) outside the surface defined by the vanishing of the electron density.     

Shortening of the nucleon''s mean free path in heavy ion collisions

The mean free path of nucleons in heavy ion collisions is most essential for the development of nuclear collective phenomena. We discuss the effect of the nucleon Fermi motion in nuclei for shortening the mean free path. This Fermi motion together with the prior Pauli effect makes nuclei nontransparent for heavy ions in the medium energy domain.