Photoionization of N2O: Mechanisms of photoionization and ion dissociation

Abstract

From high resolution photoionization mass spectrometric data on normal and isotopically substituted N2O it is concluded that the formation of NO+ below the à state of N2O+ but above the thermochemical threshold involves the calculated but hitherto unobserved 4A″ state. This state decays to NO+ from low vibrational levels, and mainly to O+ from higher levels. The O+ ion is a more important product of N2O photodissociation than previously thought. The B̃ state of N2O+ is shown to decompose to NO+ and N2+ and the C̃ state to NO+, N2+, N+, and O+. The branching in autoionization from the Ã, B̃, and C̃ Rydberg series to states of different continua has been determined and is found to depend more on the type of series than on the principal quantum number. The shapes of the resonances are strikingly different in the different final channels. The relevance of these findings to ionospheric O++N2 reaction is discussed.

A dissociative electroionization study of nitrous oxide. The no+ and N2+ dissociation channels

“…12.886 eV [8], is used to calibrate the ionizing electrons energy scale. The electron energies indicated for all the ion kinetic energy distributions presented in this work, are corrected with respect to the same reference.…”

“…In the energy range of the 2 Π state of N 2 O + , photoionization experiments [8] show the presence of several autoionization processes due to Rydberg series converging to the à 2 Σ + state. Threshold photo-electron spectra recorded in the 15-16 eV region [11] show a large number of peaks which are ascribed to quasi resonant autoionization to 2 Π in high vibrational levels.…”

“…The discrepancy with the measurement of Curran [19] at 13.75 ± 0.1 eV is noteworthy. By photoionization mass spectrometry, the threshold is measured at 14.97 eV [8] and 15.01 eV [4,5] or 15.03 eV [12].…”

“…These levels have to be populated by autoioniza-tion of superexcited states, e.g. higher members of Rydberg series [8] converging to the N 2 O + (Ã 2 Σ + ) states. Some of these have been drawn in fig.…”

“…Potts and Williams [7] recorded a He (II) photoelectron spectrum. The most recent photoionization mass spectrometric work has been performed by Berkowitz and Eland [8]. Several photoelectron [9,10] as well as threshold photoelectron-photoion coincidence [11,12] experiments have been used to investigate the dissociation of N 2 O + .…”