CO-H2O碰撞对彗星CO转动激发的影响
The effect of CO-H2O collisions in the rotational excitation of cometary CO
摘要：
本文首次给出了在5-100 K动力学温度范围内CO被H_2O转动激发的精确速率系数。将统计绝热通道方法（SACM）与高水平刚性转子CO-H2O分子间势面相结合。考虑了CO的前11个转动能级和对-H_2O和邻-H_2O的前8个转动能级之间的跃迁。我们的速率系数相比，以前的数据从文献中，他们也被纳入一个简单的非LTE模型的彗星彗发，包括碰撞引起的过渡，太阳辐射泵浦和辐射衰减。我们发现，当H2O密度在10^3-10^8 cm^-3范围内时，碰撞数据的不确定性对CO布居数分布有显著影响。我们还表明，H2O的旋转分布起着重要的作用，在CO激发（由于在CO和H2O的相关能量转移），而H2O的邻对位比的影响被发现是可以忽略不计的。
英文摘要：
We present the first accurate rate coefficients for the rotational excitation of CO by H2O in the kinetic temperature range 5-100 K. The statistical adiabatic channel method (SACM) is combined with a high-level rigid-rotor CO-H2O intermolecular potential surface. Transitions among the first 11 rotational levels of CO and the first 8 rotational levels of both para-H2O and ortho-H2O are considered. Our rate coefficients are compared to previous data from the literature and they are also incorporated in a simple non-LTE model of cometary coma including collision-induced transitions, solar radiative pumping and radiative decay. We find that the uncertainties in the collision data have significant influence on the CO population distribution for H2O densities in the range 10^3-10^8 cm^-3. We also show that the rotational distribution of H2O plays an important role in CO excitation (owing to correlated energy transfer in both CO and H2O), while the impact of the ortho-to-para ratio of H2O is found to be negligible.
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