彗星67 P中的氰、氰乙炔和乙腈及其与氰基自由基的关系
Cyanogen, cyanoacetylene, and acetonitrile in comet 67P and their relationship to the cyano radical
摘要：
氰基自由基（CN）是太空中最常被远程观测到的物质之一，彗星中也是如此。罗塞塔轨道器上的高分辨率双聚焦质谱仪（DFMS）在67 P/Churyumov-Gerasimenko彗星的内彗发中收集的数据显示了一种意想不到的化学复杂性，最近也发现了比预期更多的CN，其最有可能的母体氰化氢（HCN）的光解。本工作致力于推导相对于HCN的三个彗星腈（包括结构异构体）从DFMS数据的丰度。复杂混合物的质谱分析并不总是能够区分结构异构体。在我们的分析中，我们假设最稳定和最丰富（在类似环境中）的结构，即CHN为HCN，C2 H3 N为CH 3CN，C3 HN为HC 3 N，C2 N2为NCCN。对于氰基乙炔（HC 3 N）和乙腈（CH 3 CN），评估了完整的飞行任务时间轴，而氰（NCCN）通常低于检测限。通过仔细选择氰高于检测限的时期，我们能够跟踪NCCN和HCN之间的丰度比，从3.16 au入境到3.42 au出境。这是第一次测量彗星中的NCCN，我们发现无论是NCCN还是其他两种腈，都不足以成为CN的替代母体。
英文摘要：
The cyano radical (CN) is one of the most frequently remotely observed species in space, also in comets. Data from the high-resolution Double Focusing Mass Spectrometer (DFMS) on board the Rosetta orbiter, collected in the inner coma of comet 67P/Churyumov-Gerasimenko, revealed an unexpected chemical complexity, and, recently, also more CN than expected from photodissociation of its most likely parent hydrogen cyanide (HCN). This work is dedicated to the derivation of abundances relative to HCN of three cometary nitriles (including structural isomers) from DFMS data. Mass spectrometry of complex mixtures does not always allow distinction of structural isomers. We assumed the most stable and most abundant (in similar environments) structure in our analysis, that is HCN for CHN, CH3CN for C2H3N, HC3N for C3HN, and NCCN for C2N2. For cyanoacetylene (HC3N) and acetonitrile (CH3CN) the complete mission timeline was evaluated, while cyanogen (NCCN) often was below detection limit. By carefully selecting periods where cyanogen was above detection limit, we were able to follow the abundance ratio between NCCN and HCN from 3.16 au inbound to 3.42 au outbound. These are the first measurements of NCCN in a comet.We find that neither NCCN, nor any of the other two nitriles, is sufficiently abundant to be a relevant alternative parent to CN.
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