No abstract available

[en] A method for deconvoluting Doppler broadened positron annihilation spectra is described. The method employs a combination of an iterative technique and a curve fitting technique. The experimental data as well as the resolution function are used directly in the deconvolution process without any data smoothing and without assuming any functional form of the spectra. It has been found that components with a fwhm value of only 6% of the fwhm of the resolution function can be deconvoluted. (Auth.)

[en] Lifetime spectra have been measured for Cd at low temperatures. The results may be interpreted in terms of a temperature dependent trapping rate or an indirect trapping mechanism. (orig.)

[en] The transformation of F to R centres in KCl has been investigated by means of optical absorption and positron annihilation measurements. The intensity of the long-lived component (approximately equal to 1 ns) in the life-time spectra, which is due to annihilation in F centres, decreases with increasing R centre concentration. A simple model is proposed to explain the experimental data, from which it is indicated that annihilation in R centres takes place with a lifetime of only approximately 200 ps. The oscillator strength of the R₁ band is determined to be about 0.3. (author)

[en] Positron lifetime spectra and Doppler broadening spectra have been measured for 17 alkali halides

[en] A systematic investigation of 17 gamma-irradiated alkali halides using positron lifetime and Doppler broadening techniques has been performed. For eight of the alkali halides (NaCl, NaBr, KCl, KBr, KI, RbCl, RbBr, and RbI), a new lifetime with values between 1.0 and 1.3 ns is attributed to positrons trapped in F centres. Despite large F centre concentrations in LiF, LiCl, LiBr, and NaF, no such lifetime component is observed in these samples. Doppler broadening measurements show that in nearly all cases the momentum distribution becomes narrower upon irradiation. The experimental data are discussed in view of a recent theoretical treatment of the positron - F centre problem. (author)

No abstract available

[en] A simple correction technique for positron annihilation photon lineshape measurements which can significantly decrease systematic errors arising from resolution changes is described. (Auth.)

No abstract available

[en] Positron lifetimes have been measured in an isochronal annealing study of dynamically fatigued, high purity Cu single crystals. Decomposition of the lifetime spectra into two components results in a description of the annealing process in terms of the lifetime and fraction of trapped positrons. Positron lifetimes were also determined at a series of low temperatures (10-300 K) at different stages of annealing. The lifetime of positrons trapped at point defects is found to vary with temperature indicating that a description of the trapping process according to a simple diffusion limited model is not applicable