Department of Physics and Astronomy: Publications and Other Research
Date of this Version
1987
Citation
Published in Chemical Reviews, 1987, Vol. 87, No. 3, pp. 557-588.
Abstract
Contents
I. Introduction
II. Electron Transmission Spectroscopy
A. Background
B. Interpretation of Transmission Data
III. Alkenes, Dienes, and Polyenes
A. Ethylene and Alkyl-Substituted Ethylenes
B. Butadiene, Hexatriene, and Octatetraene
C. Other Conjugated Dienes
D. Cyclooctatetraene
E. Nonconjugated Dienes
IV. Alkynes
A. Acetylene and Alkyl-Substituted Acetylenes
B. Cyclic Acetylenes
C. Butadiyne and 2,4-Hexadiyne
V. Aromatic Systems
A. Benzene and Alkyl-Substituted Benzenes
B. Naphthalene, Anthracene, and Tetracene
C. Styrene and cis- and trans-Stilbene
D. Biphenyls
E. Triptycene, Dibenzonorbornadiene, and Related Compounds
VI. Halogen-Containing Compounds
A. Saturated Compounds
B. Unsaturated Compounds
VII. Conclusions
VIII. Acknowledgment
IX. References
X. Bibliography of Studies in ETS
The experimental methods used to characterize molecular anions differ substantially depending on the stability of the species. The application of laser spectroscopic methods, discussed elsewhere in this issue, is generally limited to anions possessing bound electronic ground states or to those with lifetimes against autodetachment of the electron in excess of a few microseconds. For a great many molecules, including such important prototypes as ethylene, butadiene, benzene, naphthalene, formaldehyde, and acetylene, the ground states of the anions are known to be unstable in the gas phase with lifetimes less than 10–12 s, typically in the neighborhood of 10–14 s. Even for those molecules with bound ground-state anions, nearly all of the excited anion states lie in the continuum and hence decay by electron detachment. Thus from consideration of numbers alone, the manifold of temporary anion states far outweighs that of stable anion states. Determination of the energies, geometries, lifetimes, and decay products of these species represents therefore a substantial and worthwhile objective. Viewed in this context, the field is the “dual” of photoelectron spectroscopy, which addresses the same characterization of cation states.
Following a description of the experimental methods and the interpretation of electron transmission data, we begin with a detailed discussion of resonances in linear polyenes. We use these to introduce the concepts used throughout the review to understand resonances and their significance to molecular orbital descriptions of molecules. Finally, at the end of the paper, we include a bibliography of papers reporting resonance data obtained with electron transmission methods. This includes all the work known to us and serves to supplement the present review.
Comments
Copyright © 1987 American Chemical Society. Used by permission.