SEARCH FOR THE DOSE-SENSITIVE OPTICALLY STIMULATED LUMINESCENCE RESPONSE IN NATURAL CARBONATES

Abstract

Carbonates of different origin, such as Iceland spar, calcites, and mollusc shells, used as electron spin resonance and thermoluminescence palaeodosimeters, were studied in order to determine their suitability for optically stimulated luminescence dating. The stimulation/excitation spectra of the afterglow of the samples were recorded in the wavelength range of 250–1100 nm. The results of the study show that these spectra present either excitation spectra of Mn2+ ion fluorescence (samples of calcites and Iceland spar, red emission recorded) or the excitation spectra of primary phosphorescence (samples of carbonates, including mollusc shells; short-wave emission bands recorded). The recorded stimulation spectra revealed no spectral bands sensitive to stimulation by ionizing radiation, which would disappear as a result of heating and could thus be related to deep traps in carbonates, needed in dating. The causes of this situation which is unusual in luminescent crystals, including luminescence (palaeo)dosimeters, and the ways of overcoming the difficulties in optical dating of natural carbonates are discussed.