Photoinduced anomalous heat generation in AgCl and AgBr single crystals at liquid-helium temperature

Abstract

Anomalous heat generation induced by band-gap light illumination was observed in AgCl and AgBr single crystals by a sensitive photocalorimetric method at liquid-helium temperature. The generated heat per second was estimated to be one to two orders of magnitude larger than the absorbed energy per second. This heat generation lasted for more than 10 h after termination of the band-gap light illumination, indicating that exothermic chain reactions were triggered by the absorbed photons. In a crystal which was not annealed, total emitted heat energy was estimated to be as high as 0.17 eV per unit cell. Consecutive nonradiative recombination of interstitial silver ions and vacancies mediated by the photoelectrons are tentatively proposed to be the responsible chain reactions. Although most of the features of the heat generation can be explained by the proposed mechanism, this mechanism requires an unrealistically high concentration of interstitial-vacancy pairs to explain the total emitted energy, leaving the observed anomalous phenomenon unexplained.

Emission Quantum Efficiency of Undoped and Eu Doped GaN Determined by Photocalorimetric Spectroscopy

“…PCS is a kind of photothermal spectroscopy, measuring the heating of a sample under illumination, due to non-radiative processes of excited carriers [2]. The details of the arrangement of PCS measurement were as stated elsewhere [3].…”

Dislocation induced absorption in silver halides

“…The increased density of SEC has been suggested by another experiment. Kondo et al repoted that the silver halide crystals subjected to the band-gap light show temperature rise as if heat is generated in the crystals and that plastic deformation of the samples strongly enhanced the temperature rise [7]. Later, they found that the temperature rise is due to the absorption of black-body radiation by the SEC by following measurements.…”