Absorptionsmessungen an LiF zwischen 0,3 und 0,9 mm Wellenl�nge

Seger, G.; Genzel, L.

doi:10.1007/bf01378284

Cited by 14 publications

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“…We have performed the transmission measurements on planeparallel specimens using a periodically working interferomc ter [3]. The radiation source was a high-pressure mercury lamp and polarization was obtained using a metal strip grating having a grating constant of 25.4 pm.…”

Section: Methodsmentioning

confidence: 99%

The Temperature Dependence of Absorption of Sodium Nitrite in the Far Infrared

Vogt

Happ

1968

Physica Status Solidi (b)

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The paper deals with the infrared absorption of ferroelectric NaNO, in the wavelength range between 350 and 1100 pm. The observed temperature dependence of absorption is attributed to one-and multiphonon processes. Below 400 "K most of the measured isochromates can be approximately described by the relation x = A T f B Ta known from multiphonon absorption in alkali halides. I n the temperature range above 400OK one expects additional defect-induced one-phonon absorption, because the onset of orientational disorder disturbes the translational symmetry of the crystal lattice. It is tried to explain the anomalies occurring in some isochromates about 450 O K by opposite temperature behaviour of one-and multiphonon absorption. I n the paraelectric phase isotherms deduced from the isochromates show selective absorption, which appears most distinctly in the ferroelectric b-direction.

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Section: Methodsmentioning

confidence: 99%

The Temperature Dependence of Absorption of Sodium Nitrite in the Far Infrared

Vogt

Happ

1968

Physica Status Solidi (b)

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“…The absorption at long wavelengths has been given special attention by Genzel and his co-workers [KLIER, 1958 (LiF);GENZEL et aI., 1958 (NaCl, KCl and KBr);SEGER and GENZEL (SEGER and GENZEL, 1962;SEGER, 1965SEGER, , 1966 (LiF), HAPP and DOTSCH, 1966 (NaCl)]. STOLEN and DRANSFELD (1965) discussed the low-temperature behavior of some alkali halides in the sub-millimeter region while OWENS (1969) looked into their high-temperature absorption.…”

Section: (12j)=[b;-bi]a(b;(qdl)b;(q2j2)bimentioning

confidence: 99%

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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On the Infra‐Red Absorption of Crystals Due to Lattice Vibrations

Wehner

1966

Physica Status Solidi (b)

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The theory of the infra‐red absorption and dispersion of crystals due to lattice vibrations is reinvestigated. Dipole moments up to third order and cubic and quartic anharmonicity in the displacements of the nuclei are considered. Using Green functions and the functional method of Martin and Schwinger a dispersion formula is derived in terms of renormalized phonons. The introduction of a renormalized linear dipole moment causes the oscillator strength to become a complex function of frequency. In the case of diatomic ionic crystals the frequency shift and lifetime of the dispersion oscillator can be obtained from the measured optical parameters.

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Absorptionsmessungen an LiF zwischen 0,3 und 0,9 mm Wellenl�nge

Cited by 14 publications

References 0 publications

The Temperature Dependence of Absorption of Sodium Nitrite in the Far Infrared

The Temperature Dependence of Absorption of Sodium Nitrite in the Far Infrared

Vibrational Infrared and Raman Spectra of Non-Metals

On the Infra‐Red Absorption of Crystals Due to Lattice Vibrations

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