Spectroscopy above the ionization threshold: Dissociative recombination of the ground vibrational level of ${\rm N}_{\rm 2}^{\rm + }$N2+

Abstract

Comprehensive theoretical calculations are reported for the dissociative recombination of the lowest vibrational level of the N(2)(+) ground state. Fourteen dissociative channels, 21 electron capture channels, and 48 Rydberg series including Rydberg states having the first excited state of the ion as core are described for electron energies up to 1.0 eV. The calculation of potential curves, electron capture and predissociation widths, cross sections and rate constants are described. The cross sections and rate constants are calculated using Multichannel Quantum Defect Theory which allows for efficient handling of the Rydberg series. The most important dissociative channel is 2(3)Π(u) followed by 4(3)Π(u). Dissociative states that do not cross the ion within the ground vibrational level turning points play a significant role in determining the cross section structure and at isolated energies can be more important than states having a favorable crossing. By accounting for autoionization, the interactions between resonances, between dissociative states, and between resonances and dissociative states it is found that the cross section can be viewed as a complex dissociative recombination spectrum in which resonances overlap and interfere. The detailed cross section exhibits a rapid variation in atomic quantum yields for small changes in the electron energy. A study of this rapid variation by future high resolution storage ring experiments is suggested. A least squares fit to the calculated rate constant from the ground vibrational level is 2.2(+0.2)/(-0.4) × 10(-7) × (T(e)/300)(-0.40) cm(3)/sec for electron temperatures, T(e), between 100 and 3000 K and is in excellent agreement with experimentally derived values.