The excitation of CO in CO-dominated cometary comae
The excitation of CO in CO-dominated cometary comae
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CO 主导的彗星彗发中 CO 的激发
DOI：
10.1093/mnras/stad268
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发表时间：
2023
影响因子：
4.8
通讯作者：
Cordiner, M.
中科院分区：
文献类型：
--
作者：
Żółtowski, M.;Lique, F.;Loreau, J.;Faure, A.;Cordiner, M.
大量的CO显着超过丰富的H2O观察彗星的彗星在大日心距离。在这些环境中，CO分子可能是最丰富的物种，因此它们可能是诱导彗星分子碰撞激发的主要抛射体。因此，它是高兴趣的CO的激发CO。本文提供了一套新的CO-CO碰撞速率系数的温度高达150 K和CO旋转levelsj 1高达10。这些数据是使用耦合态近似从量子散射计算获得的。它们被用于一个简单的辐射传输模型，以测试它们对彗星CO的激发的影响。由于相互（去）激发的目标和弹丸是重要的，CO弹丸被假定为热化的动力学温度。我们发现非定域的热力学平衡区在103- 107 cm −3的CO密度范围内扩展。我们还观察到，只要CO/H_2O比大于70%/30%，H_2O碰撞的贡献可以忽略不计。同样，CO/H2O密度比相对较低（≤ 30%/70%）时，CO对CO的激发可以忽略不计。最后，当彗发是一氧化碳和水的混合物，两者的贡献是相似的，必须加以考虑。
An abundance of CO significantly surpassing the abundance of H2O is observed in the comae of comets at large heliocentric distances. In these environments, CO molecules can be the most abundant species and they may be therefore the dominant projectiles inducing collisional excitation of the cometary molecules. It is thus of high interest to investigate the excitation of CO by CO. This article provides a new set of CO–CO collisional rate coefficients for temperatures up to 150 K and for CO rotational levelsj1up to 10. These data are obtained from quantum scattering calculations using the coupled states approximation. They are used in a simple radiative transfer model in order to test their impact on the excitation of cometary CO. Because mutual (de-)excitations of the target and projectile are important, the CO projectile was assumed to be thermalized at the kinetic temperature. We found that the non-local thermodynamical equilibrium regime extends for CO densities in the range 103–107cm−3. We also observed that as soon as the CO/H2O ratio is larger than 70 per cent/30 per cent, the contribution of H2O collisions can be neglected. Similarly, the excitation of CO by CO may be ignored for relatively low CO/H2O density ratios (≤30 per cent/70 per cent). Finally, when the coma is a ∼50 per cent/50 per cent mixture of CO and H2O, the contribution of both colliders is similar and has to be considered.