The vacuum ultraviolet spectra of the complete series of fluoroethylenes were measured from 2000 to 1150 Aring; under moderate resolution. Thepgr;*larr;pgr;transitions are easily identified in all the spectra. In most cases their maxima are only slightly displaced from their position in ethylene, but a very large hypsochromic shift is found in going from the trihyphen; to the tetrasubstituted derivative. Three Rydberg series are observed in all the spectra, converging to thepgr;ionization potential. They all exhibit vibrational fine structure dominated byCdblbnd;Cstretching and twisting vibrations. In the highly fluorine substituted ethylenes the first Rydberg band is well separated from thepgr;*larr;pgr;band (at about 1900 Aring;) as in the highly alkyl substituted derivatives. There is no evidence for transitions of sgr; electrons in this part of the spectrum except perhaps at the high frequency end of the range (1200 Aring;).
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