Electron impact spectra of ethylene, propylene, isobutene,transhyphen;butene,cishyphen;butene, trimethylethylene, and tetramethylethylene have been obtained at scattering angles of 0deg; and 90deg; and at impact energies from quest;20 to 150 eV. The spectra scan an energyhyphen;loss region from 2.5ndash;15 eV. All of the observed Rydberg transitions of the methyl derivatives are correlated to corresponding Rydberg transitions of ethylene. The missing pgr;rarr;3ptransitions of ethylene are tentatively located via this correlation. Evidence is also presented for assigning theNrarr;3Rprime; system of ethylene (at 8.26 eV) to a pgr;rarr;3pxtransition. Possible assignments of some broad continua above quest;8ndash;9eV as sgr;rarr;pgr;ast; and sgr;rarr;sgr;ast; transitions are considered. In agreement with other reported largehyphen;angle electron impact spectra, no evidence is obtained for transitions that could be assigned to triplet Rydberg states. However the pgr;rarr;pgr;ast; triplet transitions are all clearly located with transition energies in good agreement with those obtained by a variety of other techniques.
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