Experimental study of vibrational excitation of allene by slow electron impact: Vibronic coupling in the short-lived negative ion states

Journal Article · Fri Apr 15 04:00:00 EDT 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.467126· OSTI ID:6931862

Allan, M ^[1]

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1. Institut de Chimie Physique de l'Universite Fribourg, Perolles, 1700 Fribourg (Switzerland)

Vibrational electron energy loss spectra, vibrational excitation functions, and angular dependence of vibrational energy losses were measured in relative units for propadiene (allene, H[sub 2]C=C=CH[sub 2]) in an incident energy range up to 16 eV. Resonant excitation via the 2 eV resonance is not very selective; symmetric and antisymmetric C--C--C stretch, CH[sub 2] twist and scissoring, CH stretch, and C--C--C bending are all excited. The antisymmetric C--C--C stretch and CH[sub 2] twist are excited by Jahn--Teller activity of the degenerate [sup 2][ital E] resonance, the bending by vibronic coupling with higher lying resonances. The essential features of the excitation are qualitatively rationalized by a Hartree--Fock (HF)/6-31G* anion potential energy surface. Unspecific excitation of high vibrational levels, accompanied by detachment of slow electrons, is also observed to result from attachment of 2 eV electrons, and is rationalized as a consequence of temporary trapping of part of the nuclear wave packet on the bound (not autodetaching) part of the anion potential surface. Very broad resonance features are observed in the 2--16 eV range, mainly in the excitation functions of the C--H stretch and the CH[sub 2] scissoring vibrations. A moderately broad resonance peak at 11.5 eV, observed in the excitation of the symmetric and antisymmetric C--C--C stretch vibrations, is assigned to two overlapping [sigma]* shape resonances. Absolute elastic cross sections are given for reference.

• OSTI ID: 6931862
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 100:8; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
664400 -- Experimentally Derived Information on Atomic & Molecular Properties-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALLENE
ANGULAR DISTRIBUTION
ANIONS
CHARGED PARTICLES
DIENES
DISTRIBUTION
ENERGY LEVELS
ENERGY LOSSES
EXCITED STATES
FINE STRUCTURE
GROUND STATES
HYDROCARBONS
IONS
LIFETIME
LOSSES
ORGANIC COMPOUNDS
POLYENES
RESONANCE
VIBRATIONAL STATES