In luminescence dating of feldspar, laboratory induced luminescence necessary to assess the naturally acquired dose in the environment suffers from a poorly understood instability over time, known as anomalous fading (AF). AF is the source of commonly observed age underestimation in optical dating of feldspar. Approaches to circumvent AF include correction methods as well as attempts to measure directly an unfading component of feldspar luminescence, e.g. post-IR IRSL protocols. The former has the advantage of measuring the easily bleachable traps but requires extrapolations of fading rates. Post-IR IRSL methods can be limited by the use of more difficult-to-bleach traps and hence by potential age overestimations.

In this paper, we show how post-isothermal laboratory induced luminescence (pIt-IR) allows measuring an equivalent dose (D_e) that is not dependent on time elapsed since irradiation. In this procedure, one measures two IRSL signals, first from an IR stimulation at low temperature (i.e. IR₅₀) followed by a second one, at a higher temperature (i.e. IR₂₂₅). Since both signals fade at different rates, D_e from IR₅₀ is lower than that of IR₂₂₅. In pIt-IR, a succession of thermal treatments is carried out before the measurement of laboratory-induced IR₅₀ and IR₂₂₅ luminescence. The dependence of D_e on thermal annealing is different for each IR signal so one can find which thermal treatment will yield the same D_e for both signals. This D_e is assumed to be the true total radiation dose received by the feldspar minerals in nature, more properly known as the paleodose (P). This new methodology is herein applied to three samples of different ages and different geological contexts. Post-isothermal luminescence is thus proposed as a way to circumvent AF, even though extended isothermal annealing treatment is not shown to eradicate AF.

在长石的发光测年中，评估环境中自然获得的剂量所必需的实验室诱导发光遭受了人们长期以来对不稳定的理解，这被称为异常衰落（AF）。AF是长石光学测年中普遍观察到的年龄低估的来源。规避自动对焦的方法包括校正方法以及尝试直接测量长石发光的不褪色成分的方法，例如IR后IRSL协议。前者的优点是可以测量容易漂白的陷阱，但需要对衰落率进行推断。后IR IRSL方法可能会受到使用更难漂白的陷阱的限制，因此可能会因年龄过高而受到限制。

在本文中，我们展示了等温后实验室诱导发光（pIt-IR）如何允许测量等效剂量（D _e），该剂量不依赖于自照射以来经过的时间。在此过程中，一个测量两个IRSL信号，第一个测量来自低温的IR刺激（即IR ₅₀），然后第二个信号来自较高温度的IR刺激（即IR ₂₂₅）。由于两个信号以不同的速率衰减，因此IR _50的D _e低于IR _225的D _e。在pIt-IR中，在测量实验室诱导的IR ₅₀和IR ₂₂₅发光之前，先进行一系列热处理。D _e的依赖对于每个IR信号，热退火的温度都不同，因此可以发现哪种热处理将对两个信号产生相同的D _e。假定该D _e是自然界中的长石矿物所接收的真实总辐射剂量，更恰当地称为古碘（P）。本文将此新方法应用于不同年龄和不同地质背景的三个样本。因此，提出了等温后发光作为避开AF的一种方法，即使未显示延长的等温退火处理可以消除AF。