A threshold photoelectron–photoion coincidence study of the N2O+ dissociation between 15 and 20.5 eV

Abstract

Branching ratios and the kinetic energy released in the various fragmentation channels of energy selected N2O+ (15–20.5 eV) were investigated by the technique of threshold photoelectron–photoion coincidence. Pulsed synchrotron radiation from ACO, Orsay’s storage ring, dispersed by a monochromator, was used as a photon source. Threshold electrons were energy selected on the basis of angular and temporal discrimination against energetic electrons. The energy region below 16.388 eV and the ? state were investigated in detail. Below the ? state the most abundant fragment ion is O+, while above the ? state NO+ dominates. Results for the ? and ? states are also reported.

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

“…In their threshold photoelectron-photoion coincidence experiment, Nenner et al [12] do not mention energetic NO + ions below 16.5 eV. This discrepancy could be interpreted by the fact that these NO + ions are produced by dissociative autoionization where the autoionization step does not produce threshold photoelectrons (zero KE electrons).…”

“…By using the coincidence technique [9][10][11][12] it has been shown that the predissociation of the à 2 Σ + starts from its 1,0,0 level at 16.55 eV. Brehm et al [10] and Nenner et al [12] observed a large amount of kinetic energy release. These authors interpreted the broad energy release distribution, as observed at 16.55 eV, by the superposition of discrete values of kinetic energies corresponding to the formation of NO + (X l Σ + ) in the υ = 0-8 levels.…”

“…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. Threshold photoelectron-photoion coincidence experiments [12] evidenced NO + ions resulting from the dissociative autoionization of high vibrationally excited levels of the N 2 O + ( 2 Π) state. In the same experiments, the NO + time-of-flight peak indicates a narrow kinetic energy distribution, in agreement with the present results.…”

“…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].…”

“…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 + .…”