Titan harbors a dense, organic-rich atmosphere primarily composed of N₂ and CH₄, with lesser amounts of hydrocarbons and nitrogen-bearing species. As a result of high-sensitivity observations by the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6 (∼230–272 GHz), we obtained the first spectroscopic detection of CH₃C₃N (methylcyanoacetylene or cyanopropyne) in Titan’s atmosphere through the observation of seven transitions in the and rotational bands. The presence of CH₃C₃N on Titan was suggested by the Cassini Ion and Neutral Mass Spectrometer detection of its protonated form: C₄H₃NH⁺, but the atmospheric abundance of the associated (deprotonated) neutral product is not well constrained due to the lack of appropriate laboratory reaction data. Here, we derive the column density of CH₃C₃N to be (3.8–5.7)נ10¹² cm⁻² based on radiative transfer models sensitive to altitudes above 400 km Titan’s middle atmosphere. When compared with laboratory and photochemical model results, the detection of methylcyanoacetylene provides important constraints for the determination of the associated production pathways (such as those involving CN, CCN, and hydrocarbons), and reaction rate coefficients. These results also further demonstrate the importance of ALMA and (sub)millimeter spectroscopy for future investigations of Titan’s organic inventory and atmospheric chemistry, as CH₃C₃N marks the heaviest polar molecule detected spectroscopically in Titan’s atmosphere to date.

土卫六拥有浓密的，富含有机物的大气层，主要由N ₂和CH _4组成，其中烃和含氮物质的含量较少。由于Atacama大毫米波/亚毫米波阵列（ALMA）在6波段（〜230–272 GHz）中的高灵敏度观测结果，我们获得了泰坦大气中CH ₃ C ₃ N（甲基氰基乙炔或氰基丙炔）的首次光谱检测通过观察旋转带和旋转带中的七个过渡。的CH存在₃ Ç ₃ C：N于泰坦由卡西尼离子和中性质谱检测其质子化形式的建议₄ ħ ₃ NH⁺，但是由于缺乏适当的实验室反应数据，相关的（去质子化的）中性产物的大气丰度没有受到很好的限制。在这里，我们得出CH ₃ C ₃ N的柱密度为（3.8–5.7）נ10 ¹² cm ^-2基于对400泰坦中层大气以上高度敏感的辐射传输模型。与实验室和光化学模型结果进行比较时，甲基氰基乙炔的检测为确定相关的生产途径（例如涉及CN，CCN和碳氢化合物的途径）和反应速率系数提供了重要的限制。这些结果也进一步证明了ALMA和（亚）毫米波光谱法对于泰坦有机物清单和大气化学的未来研究的重要性，因为CH ₃ C ₃ N是迄今为止在泰坦大气中光谱学检测到的最重的极性分子。