Excitation of Meinel and first negative band system at the collision of electron and proton with nitrogen molecule

TL;DR

This study measures absolute cross sections for specific nitrogen molecule emissions caused by electron and proton collisions, revealing energy-independent ratios and vibrational population patterns consistent with the Franck-Condon principle, supported by theoretical estimates.

Contribution

It provides new experimental data on nitrogen excitation cross sections for electron and proton impacts in the visible spectrum, with analysis of vibrational populations and comparison to theoretical models.

Findings

Cross sections measured in the 400-1500 eV (electrons) and 0.4-10 keV (protons) energy ranges.

Ratios of Meinel to negative band cross sections are energy-independent.

Vibrational populations follow the Franck-Condon principle.

Abstract

Absolute cross sections for the $e-$N$_{2}$ and $p-$N$_{2}$ collisions for the first negative B$^{2}\Sigma_{u}^{+}-$X$^{2}\Sigma_{g}^{+}$ and Meinel A% $^{2}\Pi_{u}-$X$^{2}\Sigma_{g}^{+}$ bands have been measured in the energy region of 400-1500 eV for electrons and 0.4-10 keV for protons, respectively. Measurements are performed in the visible spectral region of 400-800 nm by an optical spectroscopy method. The ratio of the cross sections of the Meinel band system to the cross section of the first negative band system (0,0) does not depend on the incident electron energy. The population of vibrational levels corresponding to A$^{2}\Pi_{u}$ states are consistent with Franck-Condon principle. The ratio of the cross sections of (4,1) to (3,0) bands, and (5,2) to (3,0) bands exhibits slight dependence on the proton energy. The theoretical estimation within the quasimolecular approximation provides a reasonable description of the total cross section for the first negative band.