Non-LTE dust nucleation in sub-saturated vapors
Non-LTE dust nucleation in sub-saturated vapors
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亚饱和蒸气中的非 LTE 尘埃成核
DOI：
10.1111/j.1365-2966.2007.12678.x
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
D. Lazzati
中科院分区：
文献类型：
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作者：
D. Lazzati
我们用成核动力学理论研究了亚饱和蒸气中粉尘的成核特性。由于辐射损失，亚临界星系团的温度比它们的蒸气温度低。这改变了单体附着和脱离之间的动态平衡，允许颗粒在温度为亚饱和的蒸汽中稳定成核。我们发现这种效应在低密度和没有强背景辐射场的情况下特别重要。我们在n-T相图中找到了稳定形核的新条件。在非LTE区域中的成核速度可能比在过饱和蒸气中的速度慢得多。我们评估成核率，警告读者它确实依赖于在计算中假设的大分子的不可靠的性质。另一方面，形核的条件仅取决于大的稳定颗粒的性质，并且更稳健。我们最后指出，这一机制可能与早期宇宙中的尘埃污染机制有关，因为一旦星际介质被尘埃污染，扩散介质中的地幔增长很可能主导于非LTE成核。
We use the kinetic theory of nucleation to explore the properties of dust nucleation in sub-saturated vapors. Due to radiation losses, the sub-critical clusters have a smaller temperature compared to their vapor. This alters the dynamical balance between attachment and detachment of monomers, allowing for stable nucleation of grains in vapors that are sub-saturated for their temperature. We find this effect particularly important at low densities and in the absence of a strong background radiation field. We find new conditions for stable nucleation in the n-T phase diagram. The nucleation in the non-LTE regions is likely to be at much slower rate than in the super-saturated vapors. We evaluate the nucleation rate, warning the reader that it does depend on poorly substantiated properties of the macro-molecules assumed in the computation. On the other hand, the conditions for nucleation depend only on the properties of the large stable grains and are more robust. We finally point out that this mechanism may be relevant in the early universe as an initial dust pollution mechanism, since once the interstellar medium is polluted with dust, mantle growth is likely to be dominant over non-LTE nucleation in the diffuse medium.