Optical bleaching and dose-response behaviour of Al and Ti centers in quartz

Abstract

Zuccarello A. R. et al., Optical bleaching and dose-response behaviour of Al and Ti centers in quartz. (IT ISSN 0394-3356, 2011).
Electron spin resonance (ESR) is one of the most suitable methods for the dating of sedimentary events during the Quaternary.
However, in some cases, related to the specific samples under examination, ESR signals need to be previously analysed for the correct application of the methodology.
In this paper, a methodological study for ESR dating of geological sediments, by means of Aluminium (Al) and Titanium (Ti) centers in
quartz, was carried out. In this case, it is necessary to verify the optical bleaching process of ESR centers and to study the behaviour
of the corresponding signal intensity vs absorbed dose. The maximal bleaching percentage of these centers was evaluated exposing
samples to the light from a solar simulator for different times. The results showed, on the one hand, that Ti center is totally bleachable,
while the Al center is characterized by a hard to bleach component, whose evaluation is necessary to correct the ESR equivalent
dose. On the other hand, in the case of Ti-center, the growth curve of ESR signal intensity vs dose showed a trend that, for high
values, presented strong deviations from that of SSE (Single Saturation Exponential), normally used for equivalent dose determination.