Faure Alexandre, Wiesenfeld Laurent, Valiron Pierre, Tennyson Jonathan
Laboratoire d'Astrophysique, UMR 5571 CNRS, Université Joseph-Fourier, BP 53, 38041 Grenoble Cédex 09, France.
Philos Trans A Math Phys Eng Sci. 2006 Nov 15;364(1848):3113-20. doi: 10.1098/rsta.2006.1863.
Electrons are known to be efficient in rotationally exciting molecular ions in low-density astrophysical plasmas. Rotational excitation of molecular ions has also been shown to affect the measured values of dissociative recombination (DR) rate coefficients. Thus, electron collisions with H3+ are expected to play a significant role in thermalization and dissociation dynamics of this ion, both in the laboratory and in space. Using the molecular R-matrix method combined with the adiabatic-nuclei-rotation approximation, we have computed new rate coefficients for the rotational excitation of H3+ by electrons at temperatures from 10 to 10,000 K. De-excitation rates are found to amount to a few 10(-7) cm3 s(-1) below 1000 K, i.e. comparable in magnitude to that of DR. In astrophysical environments where the electron fraction exceeds 10(-4), electron collisions are thus expected to contribute to the non-thermal rotational distribution of H3+. The competition between electron and neutral collisions is discussed in the context of recent observations of H3+ towards Galactic centre sources.
众所周知，在低密度天体物理等离子体中，电子能够有效地旋转激发分子离子。分子离子的旋转激发也已被证明会影响解离复合（DR）速率系数的测量值。因此，无论是在实验室还是在太空中，电子与H3+的碰撞预计会在该离子的热化和解离动力学中发挥重要作用。利用分子R矩阵方法结合绝热核旋转近似，我们计算了在10至10000 K温度下电子对H3+进行旋转激发的新速率系数。发现在1000 K以下，去激发速率达到几10^(-7) cm³ s^(-1)，即其大小与DR相当。在电子分数超过10^(-4)的天体物理环境中，因此预计电子碰撞会对H3+的非热旋转分布有贡献。在近期对朝向银河系中心源的H3+的观测背景下，讨论了电子与中性粒子碰撞之间的竞争。
