稠密云核中氮的超分馏
Nitrogen superfractionation in dense cloud cores
摘要：
我们报告星际15 N分馏的新计算。以前，我们已经表明，大的增强15 N/14 N可以发生在寒冷，稠密的气体中，CO被冻结，但存在的NH + N通道的解离重组N2 H+严重削减分馏。鉴于最近的实验证据表明，这一渠道实际上是可以忽略不计的，我们重新评估了15 N化学致密云核。我们考虑温度低于10 K的影响，以及大量原子氮的存在。我们还展示了气相同位素比的时间演变是如何保存在氨冰地幔的空间异质性，单层沉积在不同的时间有不同的同位素组成。我们表明，这层冰的上层可能有15 N/14 N比的数量级大于底层元素值。将我们的比率转换为δ值，我们在最上层获得δ（15 N）> 3，000每密耳，在某些模型中值高达10，000每密耳。我们认为这种物质是最近在陨石和IDP中发现的15 N“热点”的前身
英文摘要：
We report new calculations of interstellar 15N fractionation. Previously, we have shown that large enhancements of 15N/14N can occur in cold, dense gas where CO is frozen out, but that the existence of an NH + N channel in the dissociative recombination of N2H+ severely curtails the fractionation. In the light of recent experimental evidence that this channel is in fact negligible, we have reassessed the 15N chemistry in dense cloud cores. We consider the effects of temperatures below 10 K, and of the presence of large amounts of atomic nitrogen. We also show how the temporal evolution of gas-phase isotope ratios is preserved as spatial heterogeneity in ammonia ice mantles, as monolayers deposited at different times have different isotopic compositions. We demonstrate that the upper layers of this ice may have 15N/14N ratios an order of magnitude larger than the underlying elemental value. Converting our ratios to delta-values, we obtain delta(15N) > 3,000 per mil in the uppermost layer, with values as high as 10,000 per mil in some models. We suggest that this material is the precursor to the 15N `hotspots' recently discovered in meteorites and IDPs
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
