Laboratory spectroscopic studies of the collisions between slow H⁺, H₂⁺, H₃⁺ions and molecular nitrogen

Abstract

Luminescence in the 275-470 nm spectral region was observed in the collisions of H + , H + 2 , and H + 3 with N 2 in the 10-1000 eV projectile energy range. For all the systems, a luminescent charge exchange leads to the electronically excited states of N + 2 (B 2 Σ u ) and N 2 (C 2 Π u , G 2 Δ g ). Computer simulation of the spectra was used to estimate relative cross sections for the reactions, as well as the temperatures corresponding to population distributions of vibrational and rotational levels of the products. The vibrational temperatures of the products for the H + 2 +N 2 and H + 3 +N 2 collision systems are found to be changing significantly with the projectile velocity, increasing from 1500 K at the lowest projectile velocities (≤50 km s −1 ) and going through a maximum (15 000 K) at about 80 km s −1 , to decrease rapidly with increasing velocity, down to 3000 K. The H + +N 2 collision system, however, does not show a similar increase in temperature. The increase in vibrational temperature indicates that, for velocities in the 50-1000 km s −1 range, the charge transfer process is the non-Franck-Condon type, a model that assumes a change in the internuclear distance of target molecule by the incident ion before electron capture occurs. This vibrational temperature dependency could be used to infer the ion velocity producing the observed emission of N + 2 . Also we found no evidence of any formation of excited NH molecules in these reactions.

Observation of the Hydrogen Migration in the Cation-Induced Fragmentation of the Pyridine Molecules

“…These observations are supported by calculations of the NH emission spectrum carried out by us, utilizing the molecular spectra simulation program. , Recently a similar computer technique, used by us in the analysis of spectra of diatomic molecules, occurring in photon- and cation-induced dissociation of five- and six-membered heterocyclic compounds, has been proven to be efficient and reliable. ,,, Thus, theoretical spectra at different vibrational and rotational temperatures have been calculated with the use of an improved set of the vibrational and rotational constants of the A 3 Π and X 3 Σ – electronic states of NH and fitted to the experimental spectrum. In these calculations the populations of the rotational and vibrational levels were assumed to follow the Boltzmann distributions.…”