Spatially resolved infrared-radiofluorescence (SR IR-RF) measurements for single-grain feldspar dating

The infrared radiofluorescence (IR-RF) signal from potassium (K)-rich feldspars has significant potential to extend the dating range beyond the limits of conventional luminescence methods. However, challenges such as poor bleachability, early saturation, and averaging effects in multi-grain aliquots have long hindered its development. Because feldspar grains vary in crystal structure, geochemistry, and luminescence behavior, single-grain analysis enables the identification and selection of grains with high dynamic range, strong bleachability, and reliable dose-response characteristics. In this study, we evaluate a newly developed CCD-based imaging system integrated with a Lexsyg Research Luminescence Reader for spatially resolved IR-RF measurements. The system detects RF signals across multiple spectral windows centered at 710, 865, 880, and 950 nm, and enables detailed analysis of individual grain dose-response curves (DRCs). Tests on two samples yielded dose recovery within ∼10% of laboratory doses. Equivalent dose ( D _e ) measurements on three natural samples using the 865 nm and 950 nm signals showed good agreement with known doses, whereas D _e from one natural sample using the 880 nm signal underestimated by ∼20%. Despite this agreement, significant overdispersion was observed, indicating substantial variability in the grain-to-grain signal. We also test a discrete dose-point acquisition approach as an alternative to continuous long-duration imaging and successfully construct typical single-grain IR-RF DRCs. This approach lowers data volume and detector noise; however, further refinement of image-processing protocols is needed for reliable use. In summary, our results highlight both the promise and challenges of single-grain IR-RF dating, emphasizing the importance of selecting grains with desirable luminescence characteristics and DRCs.