在致密分子云中模拟电子附着率对CnH -/ CnH（n= 4，6，8）柱密度比的作用
Modeling the role of electron attachment rates on column density ratios for CnH-/CnH (n=4,6,8) in dense molecular clouds
摘要：
最近在星际分子云中探测到的各种阴离子强调了现实模拟其丰度过程的重要性。为此，我们早期的计算C4 H-，C6 H-和C8 H-的辐射电子附着（REA）率产生相应的阴离子/中性（A/N）相对丰度的柱密度比。然后将后者与从观测测量中获得的结果进行比较。计算涉及的时间依赖性的解决方案的一个大型网络的化学过程在一个较长的时间间隔，并包括一系列的运行中，REA率的值被反复缩放。云建模的宏观参数也有所不同，以涵盖广泛的物理环境。结果发现，在本网络中包含的过程的范围和质量内，并从最先进的天体物理数据库中选择，与观测到的A/N比匹配所需的REA值需要减少C4 H-情况下的数量级，而C6 H-和C8 H-的相同速率只需要按小得多的因子缩放。结果表明，通常提出的星际阴离子的形成REA机制是高估了目前的模型C4 H-的情况下，这可能是一个低效的路径形成。因此，这条路径对观测到的C4 H-丰度的贡献相当小，后者更可能来自网络中的其他化学过程，正如我们在本工作中详细讨论的那样。较长的系列成员提出并在本工作中讨论的进化建模分析。
英文摘要：
(abridged) The fairly recent detection of a variety of anions in the Interstellar Molecular Clouds have underlined the importance of realistically modeling the processes governing their abundance. To this aim, our earlier calculations for the radiative electron attachment (REA) rates for C4H-, C6H-, and C8H- are employed to generate the corresponding column density ratios of anion/neutral (A/N) relative abundances. The latter are then compared with those obtained from observational measurements. The calculations involved the time-dependent solutions of a large network of chemical processes over an extended time interval and included a series of runs in which the values of REA rates were repeatedly scaled. Macroscopic parameters for the clouds' modeling were also varied to cover a broad range of physical environments. It was found that, within the range and quality of the processes included in the present network,and selected from state-of-the-art astrophysical databases, the REA values required to match the observed A/N ratios needed to be reduced by orders of magnitude for C4H- case, while the same rates for C6H- and C8H- only needed to be scaled by much smaller factors. The results suggest that the generally proposed formation of interstellar anions by REA mechanism is overestimated by current models for the C4H- case, for which is likely to be an inefficient path to formation. This path is thus providing a rather marginal contribution to the observed abundances of C4H-, the latter being more likely to originate from other chemical processes in the network, as we discuss in some detail in the present work.Possible physical reasons for the much smaller differences against observations found instead for the values of the (A/N) ratios in two other, longer members of the series are put forward and analyzed within the evolutionary modeling discussed in the present work.
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