On the analogy between local modes and color center absorption bands

Hoffmann, Helmuth

doi:10.1051/jphys:01980004104035900

Cited by 2 publications

(1 citation statement)

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“…The absorption bands of the F-and F-aggregate centres have been extensively investigated and the position of the maxima are given in the literature (for a survey see [53][54][55][56][57]). Data of several absorption bands of F-aggregate centres in different alkali halides are collected from the literature and interpreted as local vibrational modes of captured electrons in [58], because the energies of the absorption band maxima vary similar to the frequencies of the local vibrational modes of isolated H-and D-ions (called Ubands) replacing halogen ions in alkali halides [59].…”

Section: Photo Induced Reactions Of Colour Centres In Alkali Halidesmentioning

confidence: 99%

Transitions of electrons and holes drive diffusion in crystals, glasses and melts

Hoffmann

2020

Materialwissenschaft Werkst

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Diffusion of atoms or molecules (generally: particles) is driven by differences and gradients of the chemical potential of the particles in their accessible space. If the difference of the chemical potential is due to differences of concentrations alone, one arrives at the diffusion equations of Fick. The diffusion coefficients are described in known models by vibrations of atoms in condensed matter which cause the exchange of preferentially neutral particles with neighbouring particles, impurities, interstitial places and vacancies near or on surfaces, grain boundaries, dislocation lines and in the homogeneous bulk. The rates of electronic transitions, however, increase also in melts and solids of chemically bonded particles with increasing temperature. Such transitions cause large fluctuating deviations of the local energy, the charge distribution and the local chemical and electrical potentials. The fluctuating deviations interact with the core ions and drive particles to interchange. This mechanism that supplements the known mechanisms of diffusion has not yet found adequate attention in the literature until now. Foundations, experimental results, evidence and consequences for diffusion are discussed.

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Section: Photo Induced Reactions Of Colour Centres In Alkali Halidesmentioning

confidence: 99%