W. Waidelich

The influence of phonons and polarons on the infrared absorption of cadmium oxide

Abstract The infrared absorption of CdO-films with electron concentrations from 10 15 to 10 20 cm -3 was measured at 300 and 85°K up to 50μm. With increasing carrier density, the ‘classical’ spectral dependence of the electron and lattice absorption is considerably modified. At the short-wave side of the lattice band two sidebands appear. An additional absorption above the LO-lattice frequency can be explained according to the theory of Gurevich by the coupling between electrons and LO-phonons.

Thermal annealing of low-temperature X-irradiated KCl

Abstract Thermal annealing of lattice defects in KCl X-irradiated at liquid helium temperature was studied by optical absorption measurements. The annealing behaviour of the α and 195 nm bands, and of the F and H bands, respectively, can be interpreted as recombination of vacancies and interstitials.

Gitterfehlordnung in KCl mit Farbzentren

AbstractColor centers were created in KCl single crystals by additive coloration and X-irradiation at room temperature. Change of lattice parameter was determined by an X-ray method and change of mass density by a hydrostatic flotation method. Combination of these results, together with optical absorption measurements, led to the following results: F centers in additively colored KCl are Schottky defects. They cause a lattice expansionΔ v/v=0.58 perF center.F centers in X-irradiated KCl are parts of Frenkel defects. During irradiation atoms are displaced to interstitial lattice sites. The volume expansion isΔ v/v=1,15 perF center.

A trigonal color center in NaF

Uniaxial stress splitting experiments suggest the 5456 Å zero-phonon line in NaF to be due to a transition of the F3+ center. The line and a number of phonon-assisted peaks are observed in absorption and emission.

Gitterkonstanten- und Dichteänderung durchF-Zentren in KBr

F centers were created in KBr by additive coloration. Change of lattice parameter was determined by the X-ray diffraction method and change of mass density by a hydrostatic flotation method. Combination of these results led to a lattice expansion of 0.6 atomic volumes perF center. Using elastic approximation the microscopic dilatation around anF center is obtained.

Ultrarot-Absorption und phononenfreie Übergänge in strahlungsverfärbtem LiF

Spectral positions, properties and behaviour of the lines and bands found in the infrared absorption of X-rayed LiF single crystals at 90°K are investigated. Thermal annealing and optical bleaching of the crystals give informations about the correlation of the lines and the bands. Both prove to be transitions in the same absorption centre. This agrees well with the fact that the lines are due to phonon-free transitions in colour centres, whilst the bands are broadened by multiphonon processes.For the thermal annealing process of the infrared absorption a characteristic temperature of 420°K and an activation energy of 0·44 eV for the recombination process can be calculated by analysing isochrone annealing curves. According to their similar behaviour the infrared bands are compared with theR-centre absorption.

On the thermal conductivity of ammonium- and deutero-ammonium chloride

Abstract Measurements of the thermal conductivity of NH 4 - and ND 4 Cl for the temperature range 2°–300°K are presented. There is a first order phase transition in NH 4 - and probably a second order transition in ND 4 Cl.

Lattice contraction due to quenching in vacancies in platinum and gold

Abstract Combined measurements of lattice parameter and electrical resistivity change of platinum and gold after quenching were performed. The lattice contraction due to vacancies could be determined.

Evidence for Frenkel defect formation in low-temperature X-irradiated KCl and KBr

Abstract Combined measurements of lattice parameter and macroscopic length change give evidence that Frenkel defects are created in KCl and KBr during X-irradiation at 8°K.

Linear stark effect of the R-center in LiF

Abstract The change of the R2 zero-phonon line by application of electric field gives evidence for a linear Stark effect of the R-center.