Warm Carbon-Chain Chemistry
Warm Carbon-Chain Chemistry
复制标题
温碳链化学
DOI：
10.1021/cr4001308
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
and S. Yamamoto
中科院分区：
文献类型：
--
作者：
N. Sakai;and S. Yamamoto
1.1. Interstellar Clouds and Interstellar Chemistry A space between stars is not completely a vacuum, but is filled up with interstellar gas, whose average number density of H nuclei in all forms is as low as about 1 cm− 3 in the solar neighborhood. 1 Although the interstellar gas mainly consists of H and He (91% and 9% in number density, respectively), it also contains heavy elements such as C, N, O, and so on with a fraction of a few 10− 4 or less relative to the number density of H nuclei. In addition, small dust grains consisting of silicates, carbonaceous compounds, and heavy metals with a typical size of 0.1 μm are contained in the gas, whose mass fraction is about 1% of the gas. Interstellar gas is not uniformly distributed, but it often shows local condensations, called interstellar clouds, which are mainly classified into diffuse clouds and molecular clouds. Diffuse clouds have a typical density of 100 cm− 3 or less, which is exposed to interstellar ultraviolet (UV) radiation. Because of the UV radiation, H2 molecules are partly photodissociated and H atoms and H2 molecules coexist. The gas kinetic temperature of diffuse clouds is determined by a balance between UV heating (photoelectric heating) and emission cooling (by atomic and molecular transitions) and is maintained to be from 30 to 100 K. Since almost all the C atoms are ionized by photoionization due to the lower ionization potential (11.26 eV) than that of the H atoms
