论文标题
冰冷星际谷物II的蒸发冷却。关键参数
Evaporative cooling of icy interstellar grains II. Key parameters
论文作者
论文摘要
语境。当粒子突然被宇宙射线（CR）粒子或其他过程加热时，会发生冰冷星际晶粒的蒸发（升华）冷却。它导致冰冷物种的热解吸，影响星际云的化学组成。目标。我们研究有关升华冷却的详细信息，在天体化学模型中考虑此过程之前获得必要的知识。方法。我们采用了一个数值代码，该代码描述了逐层冰冷谷物的分子的升华，也考虑了在升华之前散装冰分子向表面的有限扩散。我们研究了一种谷物，突然被加热至峰值温度T，该谷物通过升华和辐射冷却。结果。回答了许多问题。如果晶粒温度t> 40k，则选择晶粒热容量C对升华分子N的数量有限。对于具有不同尺寸的晶粒，CR诱导的解吸收对于相当小的晶粒，其核心半径为〜0.02微米。 CR诱导的CO2冰的升华只有小晶粒的峰值温度为t> 80k，并且缺乏其他挥发物。 H2分子在谷物表面上的存在会加速其冷却，因此对于T <30K的其他升华分子显着降低了N。最后，如果没有扩散和随后的散装分子的升华（即，仅从表面层发生升华），则升华屈服不会超过1-2个单层，并且，如果t> 50k，n不会随着T. T. T.的增加而增加。阐明了有关冰冷星际颗粒的升华冷却的重要细节，这将使在天体化学建模中正确考虑此过程。
Context. Evaporative (sublimation) cooling of icy interstellar grains occurs when the grains have been suddenly heated by a cosmic-ray (CR) particle or other process. It results in thermal desorption of icy species, affecting the chemical composition of interstellar clouds. Aims. We investigate details on sublimation cooling, obtaining necessary knowledge before this process is considered in astrochemical models. Methods. We employed a numerical code that describes the sublimation of molecules from an icy grain, layer by layer, also considering a limited diffusion of bulk-ice molecules toward the surface before they sublimate. We studied a grain, suddenly heated to peak temperature T, which cools via sublimation and radiation. Results. A number of questions were answered. The choice of grain heat capacity C has a limited effect on the number of sublimated molecules N, if the grain temperature T > 40K. For grains with different sizes, CR-induced desorption is most efficient for rather small grains with a core radius of a ~ 0.02 micron. CR-induced sublimation of CO2 ice can occur only from small grains if their peak temperature is T > 80K and there is a lack of other volatiles. The presence of H2 molecules on grain surface hastens their cooling and thus significantly reduces N for other sublimated molecules for T < 30K. Finally, if there is no diffusion and subsequent sublimation of bulk-ice molecules (i.e., sublimation occurs only from the surface layer), sublimation yields do not exceed 1-2 monolayers and, if T > 50K, N does not increase with increasing T. Conclusions. Important details regarding the sublimation cooling of icy interstellar grains were clarified, which will enable a proper consideration of this process in astrochemical modeling.
