Autoionization in N2O as measured by angle-resolved photoelectron spectroscopy

The autoionizing decay pathways of the five-dipole allowed Rydberg series converging on the C 2 + threshold in N 2 O have been investigated using two-dimensional photoelectron spectroscopy. Measurements of electron yield as a function of both electron and photon energy have been carried out using tuneable synchrotron radiation. The vast majority of vibrational levels of the three bound electronic states of the ion that are accessible to the decaying Rydberg states have been studied with an experimental resolution of approximately 30 meV. This was sufficient to study transitions to individual vibrational levels. The comprehensive nature of the data presented has enabled various observations pertaining to both electronic and vibrational selectivity in the autoionizing decay processes to be made.The observed preference for the decay of npσ and npπ Rydberg states to the X 2 and A 2 + states of the ion respectively may be explained if the emitted electron conserves its angular momentum. Members of the ndπ series result in the most intense features in the spectrum of the only available ion state (B 2 ) that has a nuclear arrangement which is significantly different from that of the autoionizing states. It appears that dissociative, neutral states are more likely to be accessed from ndπ states and it seems plausible that these dissociative states play a role in the resonant population of the B 2 state. There is also evidence to suggest that this B 2 state has a bent equilibrium geometry.

Section: Electronic Selectivity In Autoionizing Decayssupporting

confidence: 90%

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

Sokell

Wills

Comer

et al. 1997

“…as the principal quantum number of these states increases. Additionally, Carlson et al (1985) observed that the lowest four resonances showed particularly varied angular distributions. For these reasons the autoionizing decay of these lower states warranted a study with better Table 1.…”

Section: High-resolution Photoelectron Spectramentioning

confidence: 99%

“…A preliminary investigation of the decay routes of the four lowest autoionizing Rydberg states identified by Berkowitz and Eland (1977) has been performed by Carlson et al (1985). These workers recorded constant ionic state spectra corresponding to the (0, 0, 0), (1, 0, 0) 0953-4075/96/153417+17$19.50 c 1996 IOP Publishing Ltd and (2, 0, 0) vibrational levels of the X 2 state using angle-resolved photoelectron spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

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

Sokell

Wills

Comer

1996

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.

“…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.…”

Section: Introductionmentioning

confidence: 99%

The influence of Rydberg states on the photodissociation of nitrous oxide

Shaw¹,

Holland²

2008

The absolute photoabsorption cross section and the photoionization quantum efficiency of nitrous oxide have been measured from the ionization threshold to 21 eV, using a double ion chamber and monochromated synchrotron radiation, and these have enabled the absolute photodissociation cross section to be deduced. Variations in the photoionization quantum efficiency in the vicinity of a Rydberg state have allowed the competition between predissociation and autoionization in the decay of the super-excited state to be investigated. The photodissociation cross section exhibits prominent structure which correlates with known Rydberg series. Dispersed fluorescence techniques have been employed to identify the electronically excited neutral molecular species (N 2 B 3 g and NO B 2 ) formed through photodissociation of N 2 O. Fluorescence excitation spectra due to the N 2 B 3 g → A 3 + u and the NO B 2 → X 2 transitions following excitation of N 2 O have been recorded and the features in these spectra have been compared with the corresponding structure in the photodissociation spectrum. The N 2 B 3 g fragments are produced directly through photodissociation of the parent molecule. However, at low excitation energies the NO B 2 fragments are formed only through secondary reactions. The five Rydberg series converging onto the N 2 O + C 2 + g limit are considered in detail because each series exhibits a specific decay mechanism.