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Robert, R.; Souza, M. de

doi:10.1103/physrevb.9.5257

Cited by 13 publications

(5 citation statements)

References 6 publications

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“…(with respect to the [110] direction) in-phase modes are known to coincide nearly with those of the single oscillators, i.e. the H-, Dor F centers [3,[5][6][7]. These experimental facts are in good agreement with our expectation that the coupling of neighbouring F or U centers is effective in the [110] direction, only, whereas the coupling to the surrounding lattice remains nearly unchanged.…”

supporting

confidence: 84%

“…At first we tested whether the corresponding F2, H2 and D2 center absorption band maxima E fit the relation E -m -0.5 according to equation (1). With the experimental data available from the literature [3,[5][6][7] we found always E -m-" with n close to 0.5. (with respect to the [110] direction) in-phase modes are known to coincide nearly with those of the single oscillators, i.e.…”

mentioning

confidence: 73%

“…The chief aim of the present paper is to search how well and how far this analogy holds, though we are aware of the difficulties to apply the models of a single harmonic oscillator or several coupled oscillators to color centers. However, this oversimplified model yields a crowd of predictions and relations between the different color center absorption bands, most of which tum out to be in [3,5,6,11,15,18,20].) [1,11,12,14,16,17,[19][20][21].)…”

mentioning

confidence: 99%

“…On the other hand, the aggregation of U centers needs rather refined techniques [5]. Therefore the (H-)2 and (D-)2 centers, only, which are formed by two neighbouring U centers, have been investigated in KCI, KBr, KI, NaCI, and RbCI [6]. Obviously, one can consider these centers to be built from two single local oscillators.…”

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confidence: 99%

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On the analogy between local modes and color center absorption bands

Hoffmann¹

1980

J. Phys. France

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The absorption and emission bands of F aggregate centers are compared with the local modes of H- and D- ions substituting the halogen ions in alkali halides. It is shown that the energies of the band maxima of F aggregate centers are proportional to the local vibrational mode energies of the H- or D- ions. Because of these correlations, the bands of the F aggregate centers are considered to be due to the excitation of local harmonic oscillators. From this simple picture — how oversimplified it may be — a series of predictions can be drawn, which are in fair agreement with experiment

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supporting

confidence: 84%

mentioning

confidence: 73%

mentioning

confidence: 99%

mentioning

confidence: 99%

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On the analogy between local modes and color center absorption bands

Hoffmann¹

1980

J. Phys. France

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“…Their main effect is then to contribute to the width of the line. Localized, gap and resonance vibrations due to pairs of defects have been observed in H--and D--doped alkali halides (DE SOUZA et aI., 1970;DE SOUZA and LOTY, 1973;ROBERT and DE SOUZA, 1974;ROBERT et aI., 1975;SCHNEIDER, 1974), in NaCI:Ag+ (MOLLER et aI., 1970), KCI:Na+ CLAYMAN, 1971, 1972), NaCI:F-(BECKER and MARTIN, 1972) NaCI:KF (ISHIGAMA et aI., 1972), and KI:Na+, Cl-, Be (WARD et aI., 1974;WARD and CLAYMAN, 1974a). There is some controversy of a possible defect-pair resonance observed in KI: Rb+ (WARD and CLAYMAN, 1974c) which is also interpreted as due to a maximum in the density of states (DE JONG et aI., 1973;KAPER and VANDER ELSKEN, 1975).…”

Section: I) Effects Of Defect Clusters and Defect Concentrationmentioning

confidence: 96%

Vibrational Infrared and Raman Spectra of Non-Metals

Bilz¹,

Strauch²,

Wehner³

1984

Light and Matter Id / Licht Und Materie Id

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The vibrational properties of crystals determine the photon infrared absorption, inelastic neutron scattering and, to a large extent, inelastic photon scattering by phonons, i.e., Raman scattering. The interpretation of infrared and Raman spectra requires, therefore, an understanding of the basic features of lattice dynamics. The quantum theory of solids describes the crystal properties in terms of elementary excitations and their mutual interactions. Dynamic properties are represented by phonons (lattice vibrations) and their interactions mainly with other phonons (anharmonicity), electrons (electron-phonon coupling), and photons (interaction with radiation). This characterizes the scope of the article. Its emphasis is on the interrelation between theory and experiment, i.e., on the microscopic or model interpretation of experimental spectra.Work on infrared absorption and Raman scattering of non-metallic solids was summarized twenty years ago in two review articles in this Encyclopedia by LECOMTE (1958) and by MIZUSHIMA (1958). Since then, many important new experimental data have become available, thanks to very refined techniques for measuring spectra of pure and imperfect single crystals. Furthermore, the theory of the interactions of phonons and photons has been much improved, stimulated by the remarkable development of the theory of lattice vibrations and the mathematical techniques of many-body physics.In this article we describe the dispersion and absorption of infrared radiation and Raman scattering in non-metallic crystals, both perfect and containing point defects. At present, quantitative calculations are usually restricted to diatomic crystals, especially those with simple structures such as the alkali halides or germanium and its homologues, since our knowledge of lattice vibrations is still rather poor for polyatomic and low-symmetry crystals. The theory of lattice vibrations, as reviewed by COCHRAN and COWLEY (1967) in Vol. XXV /2a of this Encyclopedia, constitutes the background and the natural starting point for our investigations. There are other recent reviews by LUDWIG (1967), COCHRAN (1971), MARADUDIN et al. (1971), SINHA (1973), and several articles in: HORTON and MARADUDIN (eds., 1974). A summary of the developments during the last few years is given in Chap. B.An important part of the theory of lattice vibrations is the construction of models. A good example is the so-called shell model for phonons (see Sect. 4) which describes the adiabatic linear electron-ion interaction in terms of localized charges and coupling constants. This provides a natural explanation of some long-range ion-ion forces in insulators in terms of induced dipole forces. Anharmonic extensions of this shell model and its modifications seem very desirable, and first attempts in this direction are discussed.Models can often give a qualitatively and sometimes quantitatively correct description of certain processes in terms of a few parameters. They provide, therefore, an orientation for microscopic approaches. Furthermo...

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