Context. Airless planetary bodies are directly exposed to solar wind ions, which can scatter or become implanted upon impact with the regolith-covered surface, while also sputtering surface atoms. Aims. We construct a semi-analytical model for the scattering of ions of hundreds of eV and the sputtering of surface atoms, both resulting in the emission of negative ions from the lunar surface. Our model contains a novel description of the scattering process that is physics-based and constrained by observations. Methods. We use data from the Negative Ions at the Lunar Surface (NILS) instrument on the Chang'e-6 lander to update prior knowledge of ion scattering and sputtering from lunar regolith through Bayesian inference. Results. Our model shows good agreement with the NILS data. A precipitating solar wind proton has roughly a 22% chance of scattering from the lunar surface in any charge state, and about an 8% chance of sputtering a surface hydrogen atom. The resulting ratio of scattered to sputtered hydrogen flux is eta_sc / eta_sp = 1.5 for a proton speed of 300 km/s. We find a high probability (7-20%) that a hydrogen atom leaves the surface negatively charged. The angular emission distributions at near-grazing angles for both scattered and sputtered fluxes are controlled by surface roughness. Our model also indicates significant inelastic energy losses for hydrogen interacting with the regolith, suggesting a longer effective path length than previously assumed. Finally, we estimate a surface binding energy of 5.5 eV, consistent with the observations. Conclusions. Our model describes the scattering and sputtering of particles of any charge state from any homogeneous, multi-species surface. Using NILS data, we successfully applied the model to update our understanding of solar wind interacting with lunar regolith, and the emission of negative hydrogen ions.

翻译：背景。无大气行星体直接暴露于太阳风离子之下，这些离子在撞击覆盖着风化层的表面时会发生散射或被注入，同时也会溅射表面原子。目标。我们构建了一个半解析模型，用于描述数百电子伏特离子的散射和表面原子的溅射过程，这两者均会导致月球表面发射负离子。我们的模型包含了一种基于物理机制并受观测约束的散射过程新描述。方法。我们利用嫦娥六号着陆器上的月球表面负离子（NILS）仪器的数据，通过贝叶斯推断更新了先前对月球风化层离子散射和溅射的认识。结果。我们的模型与NILS数据表现出良好的一致性。一个入射的太阳风质子从月球表面以任意电荷态散射的概率约为22%，而溅射一个表面氢原子的概率约为8%。对于速度为300 km/s的质子，由此产生的散射氢通量与溅射氢通量之比为eta_sc / eta_sp = 1.5。我们发现氢原子以负电荷态离开表面的概率很高（7-20%）。在近掠射角下，散射和溅射通量的角发射分布均受表面粗糙度控制。我们的模型还表明，氢与风化层相互作用存在显著的非弹性能量损失，这意味着其有效路径长度比先前假设的要长。最后，我们估算的表面结合能为5.5 eV，与观测结果一致。结论。我们的模型描述了从任何均匀、多组分表面散射和溅射任意电荷态粒子的过程。利用NILS数据，我们成功应用该模型更新了对太阳风与月球风化层相互作用以及负氢离子发射的理解。