ETHYL CYANIDE ON TITAN: SPECTROSCOPIC DETECTION AND MAPPING USING ALMA
ETHYL CYANIDE ON TITAN: SPECTROSCOPIC DETECTION AND MAPPING USING ALMA
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DOI：
10.1088/2041-8205/800/1/l14
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发表时间：
2015-02-10
影响因子：
7.9
通讯作者：
Wang, K. -S.
中科院分区：
文献类型：
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作者：
Cordiner, M. A.;Palmer, M. Y.;Wang, K. -S.
我们报告的第一次光谱检测乙腈（C2 H5 CN）在土卫六的大气中，获得使用光谱和空间分辨观测的多个发射线与阿塔卡马大毫米/亚毫米阵列（阿尔马）。土卫六电离层中存在C2 H5 CN之前是从卡西尼号的C2 H5 CNH+离子质谱测量中推断出来的。在这里，我们报告了在222-241 GHz的频率范围内检测到27条来自C2 H5 CN的旋转线（在>3 sigma置信度下检测到的19个单独的发射特征中）。同时检测多个发射线从HC 3 N，CH 3CN，和CH 3CCH也得到了。与在土卫六北方（春季）半球达到峰值的HC 3 N、CH 3CN和CH 3CCH不同，C2 H5 CN的排放被发现集中在南方（秋季）半球，这表明该物种具有明显不同的化学性质，与C2 H5 CN相对较短的化学寿命相一致。辐射传输模型表明，C2 H5 CN最集中在海拔大于或接近200公里的高度，这表明其主要产生于平流层及以上。垂直柱密度的范围为（1-5）× 10（14）cm（-2）。
We report the first spectroscopic detection of ethyl cyanide (C2H5CN) in Titan's atmosphere, obtained using spectrally and spatially resolved observations of multiple emission lines with the Atacama Large Millimeter/submillimeter Array (ALMA). The presence of C2H5CN in Titan's ionosphere was previously inferred from Cassini ion mass spectrometry measurements of C2H5CNH+. Here we report the detection of 27 rotational lines from C2H5CN (in 19 separate emission features detected at >3 sigma confidence) in the frequency range 222-241 GHz. Simultaneous detections of multiple emission lines from HC3N, CH3CN, and CH3CCH were also obtained. In contrast to HC3N, CH3CN, and CH3CCH, which peak in Titan's northern (spring) hemisphere, the emission from C2H5CN is found to be concentrated in the southern (autumn) hemisphere, suggesting a distinctly different chemistry for this species, consistent with a relatively short chemical lifetime for C2H5CN. Radiative transfer models show that C2H5CN is most concentrated at altitudes greater than or similar to 200 km, suggesting production predominantly in the stratosphere and above. Vertical column densities are found to be in the range (1-5) x 10(14) cm(-2).