A prevailing theory for the interstellar production of complex organic molecules (COMs) involves formation on warm dust-grain surfaces, via the diffusion and reaction of radicals produced through grain-surface photodissociation of stable molecules. However, some gas-phase O-bearing COMs, notably acetaldehyde (CH 3 CHO), methyl formate (CH 3 OCHO), and dimethyl ether (CH 3 OCH 3 ), are now observed at very low temperatures, challenging the warm scenario. Here, we introduce a selection of new nondiffusive mechanisms into an astrochemical model to account for the failure of the standard diffusive picture and to provide a more generalized scenario of COM formation on interstellar grains. New generic rate formulations are provided for cases where (i) radicals are formed by reactions occurring close to another reactant, producing an immediate follow-on reaction; (ii) radicals are formed in an excited state, allowing them to overcome activation barri...

中文翻译：

---

通过非扩散性粒面和冰幔化学方法在寒冷星际环境中形成复杂的有机分子

星际产生复杂有机分子（COMs）的一种流行理论涉及在温暖的尘埃颗粒表面上形成，通过稳定分子的颗粒表面光解离产生的自由基进行扩散和反应。但是，现在在非常低的温度下观察到一些气相的含O的COM，特别是乙醛（CH 3 CHO），甲酸甲酯（CH 3 OCHO）和二甲醚（CH 3 OCH 3），这给温暖的情景带来了挑战。在这里，我们将新的非扩散机制的选择引入到一个天化学模型中，以解决标准扩散图片的失败并提供星际谷物上COM形成的更一般化的情况。针对以下情况提供了新的通用费率公式：（i）自由基是由与另一种反应物接近的反应形成的，立即产生后续反应；（ii）自由基以激发态形成，从而使其能够克服活化障碍...