2019ApJ...881....3W

Fine-structure line emission from [Ne II] is observed in the infrared (12.81 µm) and could serve as a diagnostic of X-ray irradiation in protoplanetary disks. [Ne II] emission may also trace the disk gas and indicate the presence of shocks due to outflows. As the electron fraction decreases with decreasing height from the plane of a disk, collisions with atomic hydrogen begin to play an important role in populating excited fine-structure levels. We present computations of cross sections for fine-structure excitation in collisions of Ne⁺(²P) with atomic hydrogen using a fully quantal molecular-orbital close-coupling approach with complete angular momentum coupling. The results are based on accurate calculations of NeH⁺ molecular potentials obtained from the multireference single- and double-excitation configuration interaction method. We find that the excitation cross sections are dominated by resonances at energies below 1000 cm^–1. Quenching rate coefficients are given at temperatures (10-2000 K) of astronomical interest and compared with the electron impact rate.