Turner B E, Friberg P, Irvine W M, Saito S, Yamamoto S
National Radio Astronomy Observatory, USA.
Astrophys J. 1990 Jun 1;355(2):546-61. doi: 10.1086/168787.
We have made an observational study of the newly identified cyanomethane radical CH2CN and the possibly related species CH3CN with the goals of (1) elucidating the possible role of reactions of the type CnHm(+) + N in astrochemistry, and (2) providing a possible test of Bates's models of dissociative electron recombination. We find a remarkably different abundance ratio CH2CN/CH3CN in TMC-1 and Sgr B2, which we deduce is a result of the large difference in temperature of these objects. Studies of CH2CN and CH3CN in other sources, including two new detections of CH2CN, support this conclusion and are consistent with a monotonic increase in the CH2CN/CH3CN ratio with decreasing temperature over the range 10-120 K. This behavior may be explained by the destruction of CH2CN by reaction with O. If this reaction does not proceed, then CH2CN and CH3CN are concluded to form via different chemical pathways. Thus, they do not provide a test of Bates's conjectures (they do not both form from CH3CNH+). CH2CN is then likely to form via C2H4(+) + N --> CH2CNH+, thus demonstrating the viability of this important reaction in astrochemistry. The T dependence of the CH2CN/CH3CN ratio would then reflect the increasing rate of the C2H4(+) + N reaction with decreasing temperature.
我们对新发现的氰甲烷自由基CH₂CN以及可能与之相关的物种CH₃CN进行了一项观测研究，目标如下：(1) 阐明CₙHₘ⁺ + N这类反应在天体化学中的可能作用；(2) 对贝茨的离解电子复合模型进行一项可能的检验。我们发现在TMC - 1和人马座B2中CH₂CN/CH₃CN的丰度比显著不同，我们推断这是这些天体温度差异巨大的结果。对包括两次新检测到的CH₂CN在内的其他源中的CH₂CN和CH₃CN的研究支持了这一结论，并且与在10 - 120 K范围内CH₂CN/CH₃CN比值随温度降低而单调增加相一致。这种行为可能是由CH₂CN与O反应而被破坏所解释的。如果该反应不发生，那么可以得出CH₂CN和CH₃CN是通过不同的化学途径形成的结论。因此，它们无法对贝茨的推测进行检验（它们并非都由CH₃CNH⁺形成）。CH₂CN可能通过C₂H₄⁺ + N → CH₂CNH⁺形成，从而证明了这一重要反应在天体化学中的可行性。CH₂CN/CH₃CN比值对温度的依赖性将反映出C₂H₄⁺ + N反应速率随温度降低而增加的情况。
