标题： 彗星中的碱性酚氧化物 显示英文标题

标题： Alkali phenoxides in comets

摘要： 钾首次在太阳系彗星Ikeya-Seki的光谱中于近日点距离rh=0.15天文单位处被探测到，48年后，在PanSTARRS和ISON彗星中于rh=0.46天文单位处被探测到。 碱尾光离化模型提供了接近太阳值的Na/K比值。 在任何彗星中均未检测到锂：Na/Li比值的下限几乎比太阳值高一个数量级。 在这里，我们搜索了C/2020 F3和C/2024 G3彗星中的碱金属NaI、KI和LiI发射。 使用Schiaparelli天文台0.84米望远镜，在rh=0.36和0.15天文单位处获取了彗星的高分辨率光谱，这是自Ikeya-Seki以来最靠近太阳的观测。 为了模拟数据，我们假设碱性苯氧基存在于彗核表面有机尘埃的芳香族部分中，它们与二氧化碳反应释放出碱金属原子。 在两个彗星的发射线中均检测到了强度异常高的NaI和KI，但没有发现LiI发射的证据。 测定了NaI/KI比值：分别为31±5和26±8，而太阳Na/K比值为15。 这种过量及其随近日点距离的变化趋势与彗核表面CO2与碱性苯氧基之间的化学反应一致。 C/2020 F3彗星的Li上限非常严格，Na/Li > 3.4×10^4，比太阳值高34倍。 这种锂的缺失与锂苯氧基的反应速率一致，后者比钠苯氧基慢10^4倍。 碳氢化合物与有机尘埃的广泛化学作用可能在所有彗星中，包括rh > 1 au的情况下，提供显著的能量和质量CO2消耗途径，从而调和了近期彗星活动模型与罗塞塔CO2测量结果。 在rh < 0.5 au时，所有彗星中都观察到了钾，因此我们预测会形成一个空间上可分辨的KI尾部，与NaI尾部分离。 显示英文摘要

摘要： Potassium was first detected in spectra of the sungrazer comet Ikeya-Seki at the heliocentric distance rh = 0.15 au and, 48 years later, in comets PanSTARRS and ISON at rh = 0.46 au. The alkali tail photoionization model provides a Na/K ratio close to the solar value. No lithium was detected in any comet: the lower limit of the Na/Li ratio was almost one order of magnitude greater than the solar ratio. Here we searched for the emissions of the alkali NaI, KI, and LiI in Comets C/2020 F3 and C/2024 G3. High-resolution spectra of the comets were taken with the 0.84 m telescope at the Schiaparelli Observatory at rh = 0.36 and 0.15 au, the observations closest to the Sun since Ikeya-Seki. To model the data, we assumed that alkali phenoxides are present in the aromatic fraction of organic dust at the nucleus surface where they react with carbon dioxide ejecting alkali atoms. NaI and KI were detected in emission lines of exceptional intensity in both comets, with no evidence of LiI emission. The NaI/KI ratios were determined: 31 +/- 5 and 26 +/- 8, whereas solar Na/K = 15. This excess and its observed trend with the heliocentric distance are consistent with chemistry between CO2 and alkali phenoxides at the nucleus surface. The Li upper limit for comet C/2020 F3 is very stringent at Na/Li > 3.4 10^4, a factor of 34 greater than the solar value. This Li depletion is consistent with the reaction rate of lithium phenoxides, which is a factor of 10^4 slower than sodium phenoxides. The widespread chemistry of carbon dioxide with organic dust may provide a significant energy and mass sink of carbon dioxide in all comets also at rh > 1 au, reconciling recent models of cometary activity with Rosetta CO2 measurements. At rh < 0.5 au potassium was observed in all comets, so that we predict the formation of a KI tail spatially resolved from the NaI tail.