Rotational Transitions in the N2 + Ion Induced by Collisions with Helium Atoms in Cold Helium Plasmas. A Quasiclassical Trajectory Study

Abstract

Cross-sections of state-to-state rotational transitions in electronically ground-state ¹⁴ $N_2^{+}$ (X² ${\Sigma }_g^{+}$ ) ions induced by collisions with ⁴ He atoms have been calculated using a quasiclassical trajectory method and a set of artificial neural networks representing the $N_2^{+}$ /He potential energy surface. The training points for the neural networks have been calculated at a MCSCF (multi-configuration self-consistent field)/aug-cc-pVQZ level. A broad range of the $N_2^{+}$ /He collision energy has been considered ( $E_{coll}\le 100$ eV) and the efficiency of vibrational transitions in the $N_2^{+}$ ion has also been analyzed. It has been found that vibrational transitions are negligible with respect to rotational transitions up to $E_{coll}\approx 10$ eV and that above this energy, both rotational and vibrational transitions in $N_2^{+}$ are marginal in the $N_2^{+}$ /He collisions.

Keywords: cold plasma; collision dynamics; dinitrogen ion; helium; rotational excitation.