Formation of Interstellar Molecules in Gravitationally-Contracting Dark Clouds

我们研究了暗星际云和前主序星周围星周盘中分子丰度的演化。1.我们扩展了暗星际云中的gaa相反应网络模型，使其包含了372个物种，包括10个主要元素和4095个反应。该模型包含了星际化学观测研究中的大多数重要物种，新版本的数据库包含了最新的反应速率系数值。2.利用上述反应模型，我们数值计算了各种模型中分子丰度随时间的演化。结果表明，在一定的密度和温度物理条件下，气相反应可以产生大量的碳氢自由基和氰基多炔等复杂分子。具有低金属元素丰度和高离子-极性中性速率系数的模型是最可行的反应网络模型。3.研究了原恒星和金牛T星周围气体盘中分子丰度的演化。我们使用的反应网络包括气相反应，吸附到尘埃颗粒和热脱附从颗粒。冰幔中封存了大量的碳和氮，在盘的低温区，氧化冰（CO_2）和还原冰（NH_3）自然共存。

We investigate the evolution of molecular abundance both in dark interstellar clouds and in circumstellar disks around pre-main-sequence stars.1.We extend considerably the gaa-phase reaction network model in dark clouds to include 372 species which consist of 10 major elements and 4095 reactions. This model contains most of the species important in observational study of interstellar chemistry and a new version of database contains the latest values of reaction-rate coefficients.2.Using the reaction models mentioned above, we calculate numerically the pseudo-time-dependent evolution of molecular abundance in various models of dark clouds. The results show that gas-phase reactions can produce observed abundance of complex molecules such as hydrocarbon radicals and cyanopolyynes under a certain physical condition of density and temperature. Model which has low metallic elemental abundance and high ion-polar neutral rate coefficients is the most feasible one of reaction network.3.We investigate the evolution of molecular abundance in gaseous disks that are presumed to be around protostars and T Tauri stars. The reaction network we use consists of gas-phase reactions, adsorption onto dust grains and thermal desorption from grains. A considerable amount of carbon and nitrogen is locked up in the ice mantle, and oxidized (CO_2) ice and reduced (NH_3) ice naturally coexist in low temperature region of the disk.