Use of the LM-OSL technique for the detection of partial bleaching in quartz

We present a study of the sensitivity to light (ease-of-bleaching) of the t rapped charge in sedimentary quartz grains using an optically stimulated lu minescence (OSL) technique in which the intensity of the stimulation light is linearly increased during the measurement period. The technique is known as linear modulation OSL (LM-OSL). In controlled laboratory conditions, th is technique has been employed to study the ease-of-bleaching of the trappe d charge in quartz by comparing the OSL curves of quartz aliquots which hav e been either: (1) fully bleached, followed by a laboratory dose of beta -i rradiation, or (2) partially bleached, followed by the laboratory beta -dos e. The ratio of the OSL signals due to the beta -dose from the partly and f ully bleached aliquots is illustrated to be a potential indicator of the de gree of optical resetting of the OSL signal in dating material. The key par ameter governing the ease-of-bleaching is the photoionization cross-section of the trap involved. The concept is also demonstrated in a model study fr om which very good agreement with the experimental observations has been fo und. Potential applications of the technique to dating are discussed. (C) 2 000 Elsevier Science Ltd. All rights reserved.