Effects of vibronic interaction and autoionization on the photoelectron spectrum of N2O

Abstract

High-resolution and high-sensitivity HeI photoelectron spectra (PES) are reported for the first four valence levels of N2O. The vibrational structure, including many new peaks, is completely assigned for the X 2Π, A 2Σ+, and C 2Σ+ electronic states, and in all three cases excitation of a single quantum of the bending vibration is observed. The bending mode appears as a result of vibronic coupling within and between different electronic states. The Renner–Teller splitting is resolved in the (0,1,0) band of the transition to the X 2Π state. The relative intensities of the vibrational bands in the X 2Π and A 2Σ+ states are compared to the intensities determined from the threshold photoelectron spectra (TPES) of Frey et al. [Chem. Phys. Lett. 54, 411 (1978)]. In both states, autoionization of intermediate neutral states that are nearly degenerate with the molecular ion state to which they decay increases the relative intensities of the higher vibrational bands in the TPES. This resonant autoionization process can enhance bands selectively, and, in particular, the higher quanta of the symmetric stretch are systematically more intense in the TPES than in the HeI PES. New relative photoionization cross sections for N2O and its fragment ions are presented which show that even weak autoionization features can have a substantial effect on the intensities in the TPES.

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

“…This energy is close to the adiabatic ionization energy of the N 2 O + ( 2 Π), i.e. 17.45 eV [6]. The photoelectron band extends over the energy range 17.5-19.2 eV.…”

“…The threshold of 16.9 ± 0.2 eV is slightly higher, but close to the ionization potential of the à 2 Σ + state of N 2 O + which has its adiabatic ionization energy at 16.39 eV [6]. This observation would indicate the formation of NO + through the predissociation of N 2 O + (à 2 Σ + ) state through the 4 Σ -state leading to the formation of NO + by The energy range covered by portion 3 is 16.9-17.8 eV.…”

“…This observation would indicate the formation of NO + through the predissociation of N 2 O + (à 2 Σ + ) state through the 4 Σ -state leading to the formation of NO + by The energy range covered by portion 3 is 16.9-17.8 eV. The photoelectron spectrum of the à 2 Σ + state extends from 16.4 to 17 eV [6], The abovementioned interpretation could consequently only account for a part of the experimental results. A contribution of dissociative autoionization, e.g.…”

“…In the energy range of 15 eV, the ground state 2 Π of N 2 O + is known to be stable, its first excited state à 2 Σ + being at 16.39 eV [6].…”

“…The He (I) photoelectron spectrum of nitrous oxide has been investigated many times and more recently by Dehmer et al [6]. Potts and Williams [7] recorded a He (II) photoelectron spectrum.…”