New ab initio potential energy surfaces have been generated for the ground state and low-lying excited states of the H⁺ + C₃ system using the multireference configuration interaction (MRCI) method with Dunning’s augmented correlation consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis sets. The ground state and low-lying excited states show avoided crossing, indicating nonadiabatic coupling. The anisotropy of the ground-state surface has been analyzed by computing the multipolar expansion coefficients with the frozen C–C equilibrium bond length. The asymptotic potential has been merged with the interaction potential by spline fit. This potential is then used in the full close coupling calculations of rotational excitation in C₃ collision with the proton for rotational levels j = 0, 2, 4, 6, 8 at very low collision energy. By averaging the cross sections over a Boltzmann distribution of velocities of the incoming atom, we obtain and discuss corresponding rate coefficients of C₃ collision with the proton in the interstellar medium.

中文翻译：

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具有质子和旋转跃迁的量子动力学的C ₃碰撞的从头算势能面

使用多参考组态相互作用（MRCI）方法和Dunning的增强相关一致一致极化价四重ζ（aug-cc），为H ⁺ + C ₃系统的基态和低激发态生成了新的从头势能面-pVQZ）基础集。基态和低洼激发态显示出避免交叉，表明非绝热耦合。通过计算具有冻结的C–C平衡键长度的多极膨胀系数，已经分析了基态表面的各向异性。通过样条拟合将渐近势与交互势合并。然后将该电势用于C ₃中旋转激励的全封闭耦合计算在非常低的碰撞能量下，旋转量为j = 0、2、4、6、8时与质子发生碰撞。通过平均入射原子速度的Boltzmann分布上的横截面，我们获得并讨论了星际介质中C ₃与质子碰撞的相应速率系数。