Kinetic-energy distributions of O[sup [minus]] produced by dissociative electron attachment to physisorbed O[sub 2]

Journal Article · Sat Dec 31 23:00:00 EST 1994 · Physical Review A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.51.337· OSTI ID:6692690

Huels, M A; Parenteau, L; Michaud, M; Sanche, L ^[1]

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1. Groupe du Conseil de Recherches Medicales du Canada en Sciences des Radiations, Departement de Medicine Nucleaire et de Radiobiologie, Faculte de Medicine, Universite de Sherbrooke, Sherbrooke, Quebec, J1H5N4 (Canada)

We report measurements of the kinetic energy ([ital E][sub [ital k]]) distributions of O[sup [minus]] produced by low-energy electron impact (5.5--19.5 eV) on disordered multilayers of O[sub 2] physisorbed on a polycrystalline Pt substrate. The results confirm that dissociative electron attachment (DEA) proceeds via the formation of the [sup 2][Pi][sub [ital u]], [sup 2][Sigma][sub [ital g]][sup +](I), and [sup 2][Sigma][sub [ital x]][sup +](II) ([ital x]=[ital g] and/or [ital u]) states of O[sub 2][sup [minus]*]. We also find evidence for an additional resonance, namely the [sup 2][Sigma][sub [ital u]][sup +](I), positioned at about 10 eV above the neutral ground state in the Franck-Condon region, and dissociating into O[sup [minus]]+O([sup 3][ital P]). The measurements suggest that the autodetachment lifetimes of the [sup 2][Sigma][sub [ital u]][sup +](I) and [sup 2][Sigma][sub [ital g]][sup +](II) states may be longer than previously suggested. It is also observed that the effects of electron energy loss (EEL) in the solid prior to DEA, O[sup [minus]] scattering in the solid after dissociation, and the charge-induced polarization energy of the solid, broaden the [ital E][sub [ital k]] distributions, shift them to lower anion energies, and result in additional structure in them. The effects of EEL on the desorption dynamics of O[sup [minus]] are estimated from high-resolution electron-energy-loss spectra and excitation functions for losses in the vicinity of the Schumann-Runge continuum of the physisorbed O[sub 2] molecules. We find indications for an enhancement of the optically forbidden [ital X] [sup 3][Sigma][sub g][sup [minus]][r arrow]A [sup 3][Sigma][sub u][sup +] transition, and observe that the gas-phase Rydberg bands, for energy losses above 7 eV, are not distinguishable in the condensed phase.

• OSTI ID: 6692690
• Journal Information: Physical Review A; (United States), Journal Name: Physical Review A; (United States) Vol. 51:1; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
665300 -- Interactions Between Beams & Condensed Matter-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION
ANIONS
ATOMIC IONS
CHARGED PARTICLES
COLLISIONS
DETECTION
DISSOCIATION
ELECTRON ATTACHMENT
ELECTRON COLLISIONS
ELECTRON-MOLECULE COLLISIONS
ELEMENTS
ENERGY
ENERGY RANGE
ENERGY SPECTRA
EV RANGE
IONS
KINETIC ENERGY
METALS
MOLECULAR IONS
MOLECULE COLLISIONS
NONMETALS
OXYGEN
PLATINUM
PLATINUM METALS
RESONANCE
SORPTION
SPECTRA
SUBSTRATES
TRANSITION ELEMENTS