论文标题
$^{14} $ n/$^{15} $ n同位素比$ _3 $ _3 $ cn titan的气氛用阿尔玛测量
$^{14}$N/$^{15}$N isotopic ratio in CH$_3$CN of Titan's atmosphere measured with ALMA
论文作者
论文摘要
可以预期，泰坦大气中存在的每种硝化物都会表现出不同的\ ce {^{14} n/^{15} n}值取决于其生产过程，这主要是由于各种\ ce {n2}分离过程，由不同源诱导的不同来源，例如诸如紫外线辐射，磁层层层层层层层层和玻璃乳液的不同来源。对于\ ce {ch3cn}，一个光化学模型预测了下层平流层中的120--130值为120--130。这比\ ce {hcn}和\ ce {hc3n}，$ \ sim $ 67--94高得多。通过分析Atacama大毫米/亚毫米阵列（ALMA）获得的档案数据，我们成功地检测到了\ ce {CE {CH3C^{15} N}的亚毫米旋转过渡（$ j $ = 19--18）位于Titan大气层的338 GHz Band。通过将这些观察结果与同时观察到的\ ce {ch3cn}（$ j $ = 19--18）线上的349 GHz乐队的线条，从160到$ \ sim $ 400 km的海拔探测，我们随后得出了\ ce {^{14} n/^{15} n/^{15} n} 125 $^{+145} _ { - 44} $。尽管由于数据质量限制而导致的派生值范围不足，但最佳拟合值表明\ ce {^{^{14} n/^{15} n}对于\ ce {ch3cn}的值高于先前观察到的\ ce {hcn}和理论上预测的值。如最近的光化学模型所暗示的那样，这可以用不同的\ ce {n2}解离源来解释。
Each of the nitriles present in the atmosphere of Titan can be expected to exhibit different \ce{^{14}N/^{15}N} values depending on their production processes, primarily because of the various \ce{N2} dissociation processes induced by different sources such as ultraviolet radiation, magnetospheric electrons, and galactic cosmic rays. For \ce{CH3CN}, one photochemical model predicted a \ce{^{14}N/^{15}N} value as 120--130 in the lower stratosphere. This is much higher than that for \ce{HCN} and \ce{HC3N}, $\sim$67--94. By analyzing archival data obtained by the Atacama Large Millimeter/submillimeter Array (ALMA), we successfully detected submillimeter rotational transitions of \ce{CH3C^{15}N} ($J$ = 19--18) locate at the 338 GHz band in Titan's atmospheric spectra. By comparing those observations with the simultaneously observed \ce{CH3CN} ($J$ = 19--18) lines at the 349 GHz band, which probe from 160 to $\sim$400 km altitude, we then derived \ce{^{14}N/^{15}N} in \ce{CH3CN} as 125$^{+145}_{-44}$. Although the range of the derived value shows insufficient accuracy due to data quality limitations, the best-fit value suggests that \ce{^{14}N/^{15}N} for \ce{CH3CN} is higher than values that have been previously observed and theoretically predicted for \ce{HCN} and \ce{HC3N}. This may be explained by the different \ce{N2} dissociation sources according to the altitudes, as suggested by a recent photochemical model.
