Phonons inelastic properties

In diffusive point contacts (d dt> /, ) the role of the scale, where the backscattering inelastic processes become essential, turns from d in l, and in the case when li/l property will be essential when we consider the phonon structure in point-contact spectra of dirty MgB2 contacts in the c-direction. 

Photoelectron spectroscopy of valence and core electrons in solids has been useful in the study of the surface properties of transition metals and other solid-phase materials. When photoelectron spectroscopy is performed on a solid sample, an additional step that must be considered is the escape of the resultant photoelectron from the bulk. The analysis can only be performed as deep as the electrons can escape from the bulk and then be detected. The escape depth is dependent upon the inelastic mean free path of the electrons, determined by electron-electron and electron-phonon collisions, which varies with photoelectron kinetic energy. The depth that can be probed is on the order of about 5-50 A, which makes this spectroscopy actually a surface-sensitive technique rather than a probe of the bulk properties of a material. Because photoelectron spectroscopy only probes such a thin layer, analysis of bulk materials, absorbed molecules, or thin films must be performed in ultrahigh vacuum (<10 torr) to prevent interference from contaminants that may adhere to the surface. 

Coherent Inelastic Scattering.—Inelastic neutron collisions with the solid can excite phonon modes (collective vibrations) and if the coherently scattered component can be detected variation with direction within the solid, i.e. the phonon dispersion curve, can be determined. This technique is well established for bulk solids and has been used recently to examine the properties of small particles (carbon black). 

Regarding both vibrational (phonon) and magnetic (magnon) excitations, the finite particle size imposes an upper wavelength limit. This can be detected in measurements that probe the excitation spectra up to large wavelengths (e.g., inelastic neutron scattering) and it affects the thermodynamic properties of the nanoparticles. 

H. Jobic (1982). J. Chem. Phys., 76, 2693-2696. Neutron inelastic scattering from oriented and polycrystalline polyethylene observation and polarization properties of the optical phonons. 

In the present alloys Qpt equals 2kF. Under this condition, the phonon-rotons can easily interact with electrons for T > T0 causing inelastic umklapp scattering of the electrons. Below T0, only elastic umklapp scattering and inelastic scattering with normal phonons occur. Above T0, phonon-rotons can be excited thermally as well as by electron scattering. Electronic transport properties versus temperature may therefore be strongly affected (5.5.4). 

First, we will discuss concentration dependences and the scaling behaviour of these properties with Z. Later, we will discuss temperature dependencies taking into account effects due to the inelastic excitation of phonon-rotons. 

Phonons are quasiparticles, which are quantized lattice vibrations of all atoms in a solid material. Oscillating properties of the individual atoms in nonequivalent positions in a compound, however, are not necessarily equivalent. The dynamics of certain atoms in a compound influence characteristics such as the vibration of the impurity or doped atoms in metals and the rare-earth atom oscillations in filled skutterudite antimonides. Therefore, the ability to measure the element-specific phonon density of states is an advantageous feature of the method based on nuclear resonant inelastic scattering. Element-specific studies on the atomic motions in filled skutterudites have been performed (Long et al. 2005 Wille et al. 2007 Tsutsui et al. 2008). 

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