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The condition for the existence of Double Resonance effects in Raman scattering are analyzed. It is shown that the existence of points in the electronic momentum space for which both denominators in the expression for Raman scattering vanish is not sufficient. Based on this analysis, it is shown that double resonance effects cannot show up in Resonant Raman scattering in the vicinity of the E1 point in InSb.

A review is given of the scattering of coherent optical radiation in gaseous, liquid, and solid media. The spontaneous and stimulated scattering effects are considered. The direct methods for the measurement of the energy relaxation time and of the phase of the vibrations of the scattering particles are discussed. A review is also given of indirect methods based on the measurement of the frequencies, widths, and intensities of the scattering lines and of the corresponding quantities in the stimulated scattering. Practical aspects of the scattering investigations are considered, including the development of new tunable lasers.

The thermal conductivity of a number of samples of vitreous silica has been measured between 1.5 and 20 K and between 65 and 300 K. The specimens were obtained from a number of manufacturers and were all high-purity optical-quality material. Above 65 K, the thermal conductivities of all the specimens were found to be identical. Below 20 K, the thermal conductivities of four synthetic silicas, Englehard Suprasil and three types of Corning silica were the same, but the thermal conductivities of the samples made by fusing rock quartz were quite different. These differences were found to be as large as 50% at 2 K. Impurities in small concentrations have no significant effect on the thermal conductivity. According to one theory, long-range (\ensuremath{\sim} 100 \AA{}) spacial correlations in the phonon scattering resulting from the small amount of long-range order remaining in an amorphous material may be the most important factor in determining the thermal conductivity of glasses at low temperatures, and can, at least in principle, account for the difference between the various silicas.

Previous work on the low temperature thermal conductivity K of Ni doped Al2O3 single crystals has shown that Ni3+ ions give rise to resonant phonon scattering at two frequencies (T1 =.5K and T2 = 77K). The lineshape of the phonon relaxation time for the lowest resonance was shown to be quite asymetric and supposed to be due to random strains [1]. Recent work by A.P.R. and thermally detected E.P.R. has given a more precise knowledge of the energy levels; the zero-field splitting of the fundamental vibronic doublet is determined to be .68K and the tunnelling splitting δ is supposed to be large [2]. The present work concerns a study of the lineshapes of the resonant phonon relaxation times. In a first step, quantitative analysis of previous results have been done again using T1 =.68K and needs the introduction of an “intrinsic” linewidth (which was previously neglected) about 103 smaller than the strain broadened width. Two half-lorentzians,ortwo half-gaussians,givegood fits for two samples of similar Ni3+ content. The high temperature resonance is well described by an elastic scattering process. To test the validity of these lineshapes, a series of measurements in function of Ni3+ concentration has been done.

Electronic and nuclear inelastic scattering in surface channeling are studied in detail for slow ions. The transition probability of inelastic scattering is obtained as a function of the position (measured from the first atomic layer) and the scattering angle. As an example, we calculate 10- and 100-keV ${\mathrm{H}}^{+}$ ions channeled at Si(110) surface. We suggest the possibility of detecting the surface Debye temperature.

Measurements have been made using a flash thermal diffusivity technique from 550 to 2500 K on a range of well-characterized materials. Data are reported on specimens of five different porosity levels, samples in which porosity has been redistributed, and specimens, initially of two different porosity levels, oxidized to three different hyperstoichiometries. The data are discussed in the light of current theories, and it is shown that the porosity correction term is temperature-dependent. The conductivity λP at any porosity P over the temperature (T) range 500-1600 K is given by λP (W m−1 K−1) = [00433+0355P + (201+147P) × 10−4T]−1. This temperature-dependent porosity correction is shown to be related to total porosity, and it is suggested that this is due to additional vacancy scattering. An expression is derived for the additional phonon scattering due to interstitial oxygen atoms up to small hyperstoichiometry levels. Finally, the deviation from linearity at high temperatures is shown to be due to an electronic contribution to the total thermal conductivity.

The thermal conductivity of a semimetal Mg2Pb single crystal has been measured from 2 to 200 K. At low temperatures thermal conduction is by phonons limited by phonon scattering from the heavy hole Fermi surface. At higher temperatures the thermal conductivity contains both electronic and phonon contributions. A comparison of the thermal conductivity of Mg2Pb with the thermal conductivities of the related semiconductors, Mg2Si, Mg2Ge, and Mg2Sn, indicates that there is a significant bipolar contribution to the electronic thermal conductivity.

The integrated intensity of quasielastic neutron scattering by protons in polycrystalline NbH0.16 and in a single crystal of NbH0.045 was investigated as a function of the scattering vector Q. Strong deviations from a harmonic Debye-Waller factor behavior were observed at elevated temperatures. The results show a temperature dependent delocalization of the proton extending as far as the neighboring sites of the interstitial lattice. Experiments on the single crystal indicate a directional dependent mean-square amplitude of the proton even at room temperature.

The interference of the anharmonic and impurity scattering of phonons is investigated. In particular, a general formula is obtained for the resonant scattering of phonons by impurities taking into account the inelastic channel which is responsible for the temperature dependence of the total cross-section of impurity scattering. It is found that the anharmonic scattering is decreased by interference effects. The latter is connected with the finite life-time of the phonons scattered by impurities. The case of resonant scattering of phonons by isotopic defects is considered in detail. [Russian Text Ignored]

A variational method of the anisotropic scattering theory is used to analyse the drag effect of electrons by phonons and of the reciprocal drag effect on the kinetic properties of semiconductors. The role of various phonon scattering mechanisms and their effect on the thermo-e.m.f. of the drag are discussed. The temperature dependence of thermo-e.m.f. is obtained taking into account various phonon and electron scattering mechanisms. [Russian Text Ignored]

Absolute intensity measurements of the Kikuchi structures in the electron diffraction diagram (75 keV) of a thin Si single crystal have been carried out. The contributions of plasmon and quasielastic scattering have been measured separately by energy analysis. The measured line profiles and band edges are compared with the theory. From the intensity distribution due to plasmon scattering the structure potential V220 and the absorption potentials P000 and P220 could be determined. From the shape of the band edges it can be deduced that the contribution of Umklapp processes to the plasmon scattering is less than 5%. The intensity profile of the quasielastic scattering can mainly be interpreted by phonon scattering. Bei absoluten Intensitatsmessungen an Kikuchi-Strukturen im Elektronenbeugungsdia-gramm (75 keV) eines Si-Kristalls wurden die unter Plasmonenanregung und die quasi-elastisch gestreuten Elektronen mit Hilfe einer Energieanalyse voneinander getrennt regi-striert. Die geniessenen Profile von Linien und Bandkanten wurden mit den Ergebnissen tlieoretischer Arbeiten verglichen. Bei der Plasmastreunng konnten so aus der Intensitiits-verteilung das Strukturpotential V220 sowie die Absorptionspotentiale P000 und P220 bestimmt werden. Aus der Form der Bandkanten lies sich ableiten, das Umklapp-Prozesse nur an weniger als 5% der Plasmaanregungen beteiligt sind. Die Intensitatsverteilung der quasielastisch gestreuten Elektronen kann im wesentlichen durch Phononenstreuung interpretiert werden.

Raman scattering spectra of LO phonon-plasmon coupled modes were observed at various temperatures below 400 K. The contributions of plasmon damping and phonon damping were analyzed by the use of the theoretical expression of the cross section and of Hall data. The temperature dependence of the calculated LO-phonon damping was discussed.

The electrical resistivity of hexagonal synthetic single crystals and natural crystals of MoS 2 intercalated with alkali metals (K, Rb and Cs) has been measured. The average room-temperature values is 0.004 ω-cm, and the best single crystal data on K 0.4 MoS 2 showed at T 1.5 temperature behaviour characteristic of acoustical phonon scattering for a quasi-isotropic metal. The metallic behaviour and scattering mechanism are discussed.

The theory of the gain factor of the stimulated Raman scattering by polaritons in biaxial crystals is carried out in the fixed stationary pump field approximation. By sufficient length of the polariton wave vector the polariton scattering turns into the scattering by polar optical phonons which may be regarded as quasilongitudinal electromagnetic field quanta. Typical features of scattering by anisotropic polar phonons whose energy depends on the wave vector direction are investigated. Mixing of different symmetry mechanicalvibrations is analysed in anisotropic crystals. The Fermi resonance of polar mechanical phonons is studied in detail. Numerical calculations made for some particular cases agree with available experimental data. [Russian Text Ignored].

Measurements of the attenuation of high frequency ( approximately 100 GHz) phonons in copper and in superconducting aluminium are described. The phonons are generated and detected by means of superconducting tunnel junctions; a brief analysis of this novel experimental technique is included. The attenuation lengths observed are of the same order as, but rather less than, values calculated using free electron theory. The role played by elastic phonon scattering in determining the attenuation length is considered, and some measurements of the phonon propagation through granular copper presented. These can be explained in terms of the interaction of elastic and inelastic phonon scattering.

The thermal conductivity of MgO additively colored in magnesium vapor has been measured in the temperature range 1–55 K. These measurements have been compared to the pure crystal thermal conductivity data. There is a “dip” in the thermal conductivity vs. temperature curve of the additively colored specimen near 20 K, where the thermal conductivity is depressed to one-fifth of the pure crystal value. The “dip” is attributed to resonant phonon scattering associated with quasilocalized modes of theF center. After UV irradiation, resulting in partialF →F+ conversion, the thermal conductivity “dip” was found to be much weaker. The increase in thermal conductivity of the bleached sample is attributed to a relaxation of neighboring ions due to the different charge state of the defect. A successful fit to the thermal conductivity data has been made using the Debye model of solids and a defect scattering rate consisting of a resonance expression plus Rayleigh scattering term. A good fit can be made to the data of the bleached specimen by varying only the parameter associated with concentration ofF centers.

In a former paper[1], we have shown that the magnetoresistance coefficient in p -type GaSb (1+ξ) remains close to 1 at 77°K and that the mobilities ratio remains equal to 6 in the temperature range 77–300°K. We show from these results that between 30 and 300°K, the predominant scattering is a mixed scattering by lattice vibrations and ionized impurities. Interband scattering is the predominant process for light holes, while heavy holes undergo intraband scattering. In this temperature range, this mechanism accounts for the mobility variation, a result which had not been found so far on p -type GaSb.

We present data on forward and backward scattering in CuCl at liquid N2 temperature. Peaks at 146 and 172 cm-1 which appear in both forward and backward scattering spectra are attributed to other than first order scattering by optical phonons. The data on polarition scattering indicate that the atomic displacement contribution to the scattering by TO phonons is rather small. From the experimentally determined polarition dispersion curve we obtain a value of 174 ±2.5 cm-1 for ωT and a value of 5.3 for ϵS.

We elucidate the relative roles played by the accumulation space-charge region and by the skin depth in determining the magnitude of the wave vectors of the coupled LO-phonon---plasmon modes which take part in Raman scattering in $n$-InAs at the ${E}_{1}$ gap.

The calculations exhibit general features of the Umklapp process in a simple context. It is shown that the Umklapp rate is not limited by any small parameter and that special behaviour (independent of the boundary conditions) occurs at extremal points of the bands. It is also shown that interband surface scattering has only small probability for electrons in small pocket states.

This paper is concerned with the relationship between the scattering tensors for the Raman (inelastic) scattering of light by phonons, or other excitations in a crystal, and the crystal-space-group Clebsch-Gordan coefficients. It is proven that the elements of the first-order scattering tensors are a prescribed linear combination of Clebsch-Gordan coefficients; the elements of the second-order scattering tensors are a prescribed bilinear combination of Clebsch-Gordan coefficients.

Single crystals of argon were grown and investigated at 82.3 K, near the triple point. X-ray diffraction photographs taken in transmission were used to verify that the crystals were single and to determine their orientation. Brillouin spectra were obtained for several different orientations of three crystals. The observed spectra contained the longitudinal component and at least one, and sometimes both transverse components. Their frequency shifts were used to determine the adiabatic elastic constants at 82.3 K: ${C}_{11}=2.38\ifmmode\pm\else\textpm\fi{}0.04$, ${C}_{12}=1.56\ifmmode\pm\else\textpm\fi{}0.03$, ${C}_{44}=1.12\ifmmode\pm\else\textpm\fi{}0.03$, in units ${10}^{10}$ dyn/${\mathrm{cm}}^{2}$, and the elastic anisotropy $A=2.73\ifmmode\pm\else\textpm\fi{}0.10$. These values differ significantly from earlier results derived from neutron scattering and ultrasonic experiments. However, there is good agreement with recent Monte Carlo calculations which use multiparameter pair potentials and the triple-dipole interaction.

The thermal conductivities of superconducting Nb and Ta have been measured in the temperature range 0.04-4 K with and without the presence of dissolved H or D. In Nb doped with D the phonon mean free path exhibits a minimum which occurs at the same temperature at which a deuterium-related anomaly has been observed in the specific heat. Phonon scattering caused by the addition of H to Nb or Ta is complicated by the presence of resonant scattering from dislocations produced by precipitation of the $\ensuremath{\beta}$-phase hydride.

The thermal conductivity of a borosilicate glass has been measured in the temperature range 0.05-50 K. The samples contained well-defined holes to provide a source of phonon scattering. The results are consistent with the predictions of the Debye model using experimentally measured sound velocities. The results also indicate that thermal transport at temperatures below \ensuremath{\approx} 30 K is provided by low-frequency phonons having a characteristic temperature \ensuremath{\lesssim} 3 K.

The drift and Hall mobility of electrons in 10M NaOH glassy alkaline ice has been studied to determine the relevant charge transport mechanisms in this disordered system. The electrons are photoexcited to a conduction state after being trapped in the matrix at 77 K by γ irradiation. The dominant electron scattering mechanisms have been deduced from variation of voltage and temperature, and it appears that electron transport in this matrix is well characterized by a band model. Field dependent mobilities are observed and indicate that hot electron effects exist. In the field independent mobility region, the limit of which depends on temperature, the dominant mechanism is scattering by acoustical and optical phonons. This holds above 77 K and probably to much lower temperatures. In the field dependent mobility region, the dominant mechanism is ionic species scattering, notably by O−, at lower temperatures, and acoustical and optical phonon scattering at higher temperatures. The dividing temperature decrease...

Thermoelectric power (S) measurements have been made on several supersaturated AlMn alloys containing up to 2 at.% Mn in solid solution. The Mn contribution has been obtained from 2 to 440K to an accuracy of +or-5% by making corrections for phonon scattering and phonon drag. The results are compared with data for the more strongly magnetic alloys, CuFe, AuV and AuCo, by plotting S/SN against T/ Theta R, where Theta R is the characteristic temperature from the -T2 term in the low temperature electrical resistivity (except for AuCo), and SN is a normalization factor. The data for all the alloys lie on the same curve in the temperature range considered, (T/ Theta R

The lattice scattering limited mobility of electrons in GaAs as well as the scattering (Hall) factor is calculated for a very wide temperature range extending from liquid helium temperatures up to about the melting point. It is shown that at temperatures above about 100 K the polar optical phonon scattering dominates the mobility and below about 80 K the piezoelectric scattering is dominant. The deformation potential scattering plays an important role at around 80–100 K and at the highest temperatures. The calculated mobility curves are extensively compared with the results of other similar calculations. The results of mobility calculations agree well with the relevant experimental data.

An analysis of elastic electron scattering from the nuclear charge and magnetization distributions is carried out with phase-shift analysis and distorted-wave Born approximation, respectively. We find that magnetic electron scattering should be measurable from medium and heavy odd-$A$ nuclei at normal scattering angles in addition to 180\ifmmode^\circ\else\textdegree\fi{}. In particular, the scattering from the maximally allowed magnetic multipole distribution should be easily observed.

We have investigated the nonohmic resistivity of a nondegenerate semiconductor in quantizing magnetic fields for the case where acoustic phonons are the dominant scattering mechanism. The type of I-V characteristics found depends upon which of three mechanism are dominant. The three mechanisms are due to collisional broadening, inelasticities due to the finite phonon energy and phonon drag. When collistion broadening is important, the nonlinearities in the current voltage characteristic arise only from electron heating, while when the inelasticities are dominant, there is also an intrinsic nonlinearity in the characteristic. Finally, when phonon drag is dominant, high frequency acoustoelectric amplification will occur when the Hall velocity exceeds the sound velocity, i.e. VH > S. For the case where inelasticities dominate, a region of negative differential resistance is obtained that should persist even when there is considerable optical phonon scattering.

Comprehensive measurements of the orbitally averaged scattering rate characterized by the Dingle temperature have been carried out for a number of orbits in dilute alloys of copper containing nickel, germanium or gold as solute. By combining the data for orbits traversing different regions of the Fermi surface and using a Fourier series inversion scheme, characteristic maps depicting the anisotropy of the local electron-impurity scattering rate 1/ tau *(k) over the Fermi surface have been deduced for each type of impurity scattering centre. The maps show a pronounced anisotropy which is different for each of the three solutes. The results may be understood in terms of the partial wave scattering model of Coleridge, and enable the differences Delta eta 1 between the phase shifts characterizing the host and impurity potentials to be determined.

In the strong coupling theory the interaction potential is obtained in the nonrelativistic approximation. (auth)

Phonons in AgBr are studied by neutron inelastic scattering along the [111] direction of reciprocal lattice. From the phonon dispersion and the optical data, it is concluded that the valence band maximum is at the L -point and the phonons participating in the indirect band-gap transition are identified as TO( L ) and LA( L ).

The properties of interference between the one and multiphonon contributions to the dynamic and static scattering functions, S(Q, ω) and S(Q), first considered by Ambegaokar et al., are discussed in detail for b.c.c 3He and 4He for comparison with recent neutron and proposed X ray scattering experiments. Calculations of interference for Na and of the Debye temperature appropriate to the Debye–Waller factor in b.c.c 3He are also presented. In all cases the on shell interference term which alters the one phonon scattering intensity is found to be more important than the off shell term which alters the one phonon line shape. This is characteristic of systems in which anharmonic effects produce a large phonon frequency shift but in which the phonon lifetimes remain long. The difficulty in establishing the one phonon sum rules experimentally in the presence of interference is emphasized. As noted by Horner, existing unusual variations of scattering intensity observed in solid 4He can be satisfactorily explained by taking account of interference and this difficulty without introducing an anomolous Debye–Waller factor. Comparisons with liquid 4He suggest a similar difficulty in establishing the sum rules there.

The scattering dependence of electroacoustic amplification is studied in this paper together with the effect of a longitudinal magnetic field in the extreme quantum limit, when only the lowest Landau level is occupied by the electrons. As in the case of absorption, the magnetic field enters this theory only through its effect on the electronic relaxation time. A numerical-example is discussed for the two cases in which the electronic relaxation time is given bya) acoustic-phonon scattering andb) ionized-impurity scattering. At frequencies outside the domain of validity of the local theory (ql τ 1), the absorptionamplification coefficient is found to be strongly scattering dependent. In particular the threshold value of the drift velocity to obtain amplification may be very different from, and even one order of magnitude higher than, the sound velocity.

An expression is obtained for the relaxation time for scattering of phonons by platelets of precipitated impurities of atomic masses and volume different from the host. For large-diameter platelets a closed expression was used in a model describing plateletlike nitrogen precipitates in type-$\mathrm{I}a$ diamonds. A fit of the model to thermal-conductivity data reported by Slack indicates that the major fraction of nitrogen impurities are present in nonparamagnetic point-defect associations rather than in large precipitates, at least for that specimen. The minor fraction of nitrogen present as platelets governs the thermal conductivity at very low temperatures.