A study of vibrational selectivity of electronic autoionization processes in using two-dimensional photoelectron spectroscopy

Abstract

Two-dimensional photoelectron spectroscopy has been used to investigate vibrational selectivity accompanying electronic autoionizing decays of Rydberg states between the and ionization thresholds in . Measurements of electron yield as a function of both electron and photon energy have been carried out using tuneable synchrotron radiation. This study, which is the most comprehensive to date, has enabled the vast majority of the accessible vibrational levels of the ion to be investigated. The experimental resolution was good enough to observe individual vibrational levels and complex vibrational selectivity was evident throughout the two-dimensional spectrum. A significant number of the features in the spectrum could be ascribed to vibrational progressions in the symmetric stretch mode.

A two-dimensional study of the autoionizing decay routes of Rydberg states converging on the ionization threshold in

“…As the nuclear arrangement of the Rydberg states converging on the C 2 + ionic state are in turn assumed to be similar, only the lowest vibrational levels of the X 2 and A 2 + are accessible to Franck-Condon autoionizing transitions from these Rydberg states. This behaviour is also expected for the Rydberg states which converge upon the A 2 + state (Sokell et al 1996). However, approximately 10% of the autoionizing decays of the lower-lying (7σ −1 ) Rydberg series are observed to populate higher than anticipated vibrational levels of the X 2 state (Baer et al 1979).…”

“…Although non-Franck-Condon resonant autoionization processes do not appear to play a very significant role in the decay of the Rydberg states converging on the C state of the N 2 O + ion, there is evidence of these non-vertical transitions in the 2DPES of figures 2 and 4. There are horizontal bands extending to threshold visible in the spectrum of the B state (figure 4), rather like those that occur in the Franck-Condon gap between the X and the A states of the ion (Sokell et al 1996). It seems likely that a mechanism similar to that which populates high vibrational levels of the X state in the Franck-Condon gap is responsible for the production of low-energy electrons at these higher photon energies.…”

“…It forms the second part of a study of the photoprocesses in this molecule. The autoionizing decay of Rydberg states converging on the lower, A 2 + threshold has been dealt with in a previous two-dimensional study (Sokell et al 1996). The arrangement of the 22 electrons in the ground state of the N 2 O molecule is (1σ ) 2 (2σ ) 2 (3σ ) 2 (4σ ) 2 (5σ ) 2 (6σ ) 2 (1π) 4 (7σ ) 2 (2π) 4 .…”

Decay pathways of superexcited states of nitrous oxide

“…Nitrous oxide has 22 electrons, and its groundstate electronic configuration can be written as (1σ) 2 (2σ) 2 (3σ) 2 (4σ) 2 (5σ) 2 (6σ) 2 (1π) 4 (7σ) 2 (2π) 4 . Extensive experimental works have been conducted to study the superexcited states of N 2 O, most of which were carried out by: photoabsorption, [4][5][6] photoionization, [7][8][9][10] photoelectron energy spectroscopy, [11][12][13][14] photoionization mass spectroscopy, [7,15,16] photon-induced fluorescence, [9,[17][18][19] and photoelectron-photoion coincidence spectroscopy. [20][21][22] Among these, the cross sections of the structured ionization region and their decay pathways have been investigated by Refs.…”

The influence of Rydberg states on the photodissociation of nitrous oxide

“…Autoionization and predissociation have long been recognized as competitive channels in the decay of super-excited states [2]. Most of the experimental work investigating this competition in N 2 O has focused on autoionization, and numerous studies using photoelectron spectroscopy [3][4][5][6], mass spectrometry [7][8][9][10] and fluorescence spectroscopy [11][12][13][14][15][16] have enabled a good understanding of the way in which autoionization affects the valence shell photoionization dynamics to be obtained.…”