Electron/molecular cation collisions in low-temperature plasmas: from mechanisms to rate coefficients

The kinetics of various cold ionized media is driven by electron-impact dissociative recombination, dissociative excitation and ro-vibrational (de)excitation of molecular cations [1]. These collisions are highly reactive, involve numerous super-excited molecular states undergoing predissociation and/or autoionization, and their measurement and modeling both result in cross sections desplaying a strong resonant character. Their theoretical study requires sophisticated methods capable to go far beyond the Born-Oppenheimer approximation, and to manage to describe a complex molecular dynamics relying on the superposition of many continua and infinite series of Rydberg states. We have used the Multichannel Quantum Defect Theory (MQDT) in order to compute cross sections and rate coefficients for the invoked processes for H$_2^+$, H$_3^+$, N$_2^+$ [2], BeH$^+$ [3], BF$^+$, NO$^+$, CO$^+$, SH$^+$, CH$^+$ and ArH$^+$, and we have compared them with the experimental ones - obtained in storage rings and flowing afterglows. [1] I. F. Schneider, O. Dulieu, and J. Robert (editors) 2015, Eur. Phys. J. Web of Conf., http://www.epjconferences.org/articles/epjconf/abs/2015/03/contents/contents.html, 84. [2] D. A. Little et al. 2014, Phys. Rev. A 90, 052705. [3] V. Laporta et al., 2017 Plasma Phys. Contr. Fusion 59, 045008.