The CH$_\mathsf{2}$CN - molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?
The CH$_\mathsf{2}$CN - molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?
复制标题
CH$_mathsf{2}$CN - 分子：$mathsf{lambda}$8037 弥漫星际带的载体？
DOI：
10.1051/0004-6361:20077358
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发表时间：
2007
影响因子：
6.5
通讯作者：
Cordiner M
中科院分区：
文献类型：
--
作者：
Cordiner M
参考新的观测数据，检验了氰乙基阴离子ch2cn -负责Å相对狭窄的弥漫星际带（DIB）的假设。在2.7 K的旋转温度下，利用文献中的光谱参数计算了阴离子从电子基态跃迁到第一偶极束缚态的吸收带，得到了峰值波长为8037.78 Å的旋转轮廓线。通过与8条重变红的银河系视线的漫射带和原子线吸收光谱的比较，发现ch2cn -是λ8037漫射星际带的可能载体，前提是旋转轮廓是多普勒加宽的，参数在16到33 km s-1之间，这取决于特定的视线。计算的ch2cn -跃迁与星际光学深度剖面的卷积结果与观测到的HD 183143， HD 168112和Cyg ob28a的窄λ8037 DIB剖面很好地匹配。旋转能级居群可能受到核自旋统计量的影响，导致在8025和8050 Å附近的邻位ch2cn -出现在目前可用的星际光谱中未见的额外跃迁。要使ch2cn成为λ8037漫射星际带的载流子，a)必须存在将ch2cn从邻位元转换为对构相的机制，或者b)形成ch2cn的化学反应必须导致接近3 K附近玻尔兹曼分布的能级群。
The hypothesis that the cyanomethyl anion CH2CN-is responsible for the relatively narrow diffuse interstellar band (DIB) at Å is examined with reference to new observational data. The absorption band arising from the transition from the electronic ground state to the first dipole-bound state of the anion is calculated for a rotational temperature of 2.7 K using literature spectroscopic parameters and results in a rotational contour with a peak wavelength of 8037.78 Å. By comparison with diffuse band and atomic line absorption spectra of eight heavily-reddened Galactic sightlines, CH2CN-is found to be a plausible carrier of theλ8037 diffuse interstellar band provided the rotational contour is Doppler-broadened with abparameter between 16 and 33 km s-1that depends on the specific sightline. Convolution of the calculated CH2CN-transitions with the optical depth profile of interstellar results in a good match with the profile of the narrowλ8037 DIB observed towards HD 183143, HD 168112 and Cyg OB2 8a. The rotational level populations may be influenced by nuclear spin statistics, resulting in the appearance of additional transitions from of ortho CH2CN-near 8025 and 8050 Å that are not seen in currently available interstellar spectra. For CH2CN-to be the carrier of theλ8037 diffuse interstellar band, either a) there must be mechanisms that convert CH2CN-from the ortho to the para form, or b) the chemistry that forms CH2CN-must result in a population of levels approaching a Boltzmann distribution near 3 K.