乙烯和乙烷的CN与CCH衍生物：TMC-1中CH$_3$CH$_2$CCH探测的确认
CN and CCH derivatives of ethylene and ethane: Confirmation of the detection of CH$_3$CH$_2$CCH in TMC-1
AI总结：
本研究利用QUIJOTE谱线巡天确认TMC-1中存在CH$_3$CH$_2$CCH，测定了多种乙烯、乙烷衍生物的丰度比及碳同位素比值，修正了CH$_2$CHCN的$b$型偶极矩，并用气相反应化学模型解释了观测丰度。
摘要：
我们利用QUIJOTE$^1$（基约特）谱线巡天对TMC-1中的CH$_3$CH$_2$CCH、CH$_3$CH$_2$CN、CH$_2$CHCCH和CH$_2$CHCN开展了研究。我们确认了TMC-1中存在CH$_3$CH$_2$CCH，该分子此前由我们团队报告为疑似探测结果。通过对TMC-1中CH$_2$CH$_2$和CH$_3$CH$_3$的乙炔基与氰化物衍生物的详细研究，我们发现CH$_2$CHCCH/CH$_2$CHCN与CH$_3$CH$_2$CCH/CH$_3$CH$_2$CN的丰度比分别为1.5$\boldsymbol{\u00b1}$0.1和4.8$\boldsymbol{\u00b1}$0.5。推导得到的CH$_2$CHCCH/CH$_3$CH$_2$CCH丰度比为15.3$\boldsymbol{\u00b1}$0.8，而CH$_2$CHCN与CH$_3$CH$_2$CN的丰度比为48$\boldsymbol{\u00b1}$5。我们探测到了乙烯基氰的所有单取代同位素异构体，并且发现CH$_2$CHCN中第一位和第二位碳取代得到的$^{12}$C/$^{13}$C比值，与HCCNC和HNCCC等其他含三个碳的分子的比值一致。然而，第三种$^{13}$C同位素异构体CH$_2$CH$^{13}$CN的丰度有所升高，这一现象与HCCCN的情况类似。最后，我们观测到了CH$_2$CHCN的8条$b$型跃迁，发现采用此前推导的偶极矩$μ_b$无法拟合这些跃迁的强度。这些跃迁涉及的转动能级与$a$型跃迁的转动能级相同。根据其强度，我们得到$μ_b$=0.80$\boldsymbol{\u00b1}$0.03 D，该值介于实验室中利用强度测量或斯塔克效应推导的早期数值之间。我们的化学模型表明，TMC-1中观测到的CH$_3$CH$_2$CCH、CH$_3$CH$_2$CN、CH$_2$CHCCH和CH$_2$CHCN的丰度可以通过气相反应来解释。
英文摘要：
We present a study of CH$_3$CH$_2$CCH, CH$_3$CH$_2$CN, CH$_2$CHCCH, and CH$_2$CHCN in TMC-1 using the QUIJOTE$^1$ line survey. We confirm the presence of CH$_3$CH$_2$CCH in TMC-1, which was previously reported as tentative by our group. From a detailed study of the ethynyl and cyanide derivatives of CH$_2$CH$_2$ and CH$_3$CH$_3$ in TMC-1, we found that the CH$_2$CHCCH/CH$_2$CHCN and CH$_3$CH$_2$CCH/CH$_3$CH$_2$CN abundance ratios are 1.5$\pm$0.1 and 4.8$\pm$0.5, respectively. The derived CH$_2$CHCCH/CH$_3$CH$_2$CCH abundance ratio is 15.3$\pm$0.8, and that of CH$_2$CHCN over CH$_3$CH$_2$CN is 48$\pm$5. All the single substituted isotopologs of vinyl cyanide have been detected, and we found that the first and second carbon substitutions in CH$_2$CHCN provide a $^{12}$C/$^{13}$C ratio in line with that found for other three-carbon bearing species such as HCCNC and HNCCC. However, the third $^{13}$C isotopolog, CH$_2$CH$^{13}$CN, presents an increase in its abundance similar to that found for HCCCN. Finally, we observed eight $b$-type transitions of CH$_2$CHCN, and we find that their intensity cannot be fitted adopting the dipole moment $μ_b$ derived previously. These transitions involve the same rotational levels as those of the $a$-type transitions. From their intensity, we obtain $μ_b$=0.80$\pm$0.03\,D, which is found to be in between earlier values derived in the laboratory using intensity measurements or the Stark effect. Our chemical model indicates that the abundances of CH$_3$CH$_2$CCH, CH$_3$CH$_2$CN, CH$_2$CHCCH, and CH$_2$CHCN observed in TMC-1 can be explained in terms of gas-phase reactions.
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