Photoemission yield (the number of emitted electrons per incoming photon) is one of the fundamental properties of solid materials but is not yet well constrained for the lunar surface for photon energies >∼20 eV. In this study, we constrain this yield for incident photons with energies of ∼10–500 eV with data from the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission along with solar irradiance spectra from Version 2 of the Flare Irradiance Spectral Model. We also report the first oxygen Auger electron observations at the Moon by the ARTEMIS spacecraft, which provides a unique feature to identify photoelectrons emitted from the lunar surface. With lunar photoelectron observations identified in both Earth's magnetotail lobes and the solar wind for four selected days, we infer a lower bound of 10⁻³ in yield for photon energies >∼20 eV. However, our investigation also reveals an uncertainty over ∼4 orders of magnitude in derived yields with a sensitivity study, owing to a poorly constrained photoelectron energy probability function. This uncertainty motivates future experiments on lunar samples to better characterize the lunar surface charging environment.

中文翻译：

---

从 ARTEMIS 测量推断的月球光电发射产率

光发射产率（每个入射光子发射的电子数）是固体材料的基本特性之一，但对于光子能量 >~20 eV 的月球表面还没有得到很好的限制。在这项研究中，我们使用来自月球与太阳相互作用的加速、重联、湍流和电动力学 (ARTEMIS) 任务的数据以及来自第 2 版的太阳辐照度光谱来限制能量为 10–500 eV 的入射光子的这一产量耀斑辐照度光谱模型。我们还报告了 ARTEMIS 航天器在月球上的第一次氧俄歇电子观测，它提供了一个独特的功能来识别从月球表面发射的光电子。在选定的四天里，在地球的磁尾瓣和太阳风中都发现了月球光电子观测结果，光子能量>~20 eV 的产率为^-3。然而，由于光电子能量概率函数的约束很差，我们的研究还揭示了通过敏感性研究得出的产率超过 4 个数量级的不确定性。这种不确定性促使未来对月球样本进行实验以更好地表征月球表面充电环境。