Time-resolved luminescence from feldspars: New insight into fading

Time-resolved infrared optically stimulated luminescence (IR-OSL) signals of K- and Na-feldspar samples extracted from sediments were measured in UV, blue and red detection windows, using a fast photon counter and pulsed IR stimulation (λ=875nm). We observe that the relative contribution of long lifetime (∼20μs) components in K-feldspars is greater than that in Na-feldspars at each detection wavelength. From any one feldspar sample, red and blue IR-OSL signals have a greater contribution of long lifetime components than UV IR-OSL. We found this long lifetime component was significantly more stable than shorter lifetime components, by comparing natural/regenerated and prompt/delayed time-resolved IR-OSL. We also compared both pulsed and continuous wave (CW) equivalent dose (De)(De) values from four feldspar samples. For pulsed IR-OSL, the signal was collected between 10 and 100μs after the diodes were switched off, to avoid all contributions from short lifetime components. In all cases, the pulsed DeDe values were larger than the CW DeDe values, regardless of the type of the feldspar and the detection wavelength; the pulsed DeDe values were also all consistent with those calculated from the quartz DeDe. It is possible that the long lifetime component from feldspars do not show anomalous fading.