The vacuum ultraviolet spectra of methyl and ethyl cyanide have been determined in the region 1000A to 1800A. Three members of a Rydberg series were found for methyl cyanide starting at 1292A, the limit of the series corresponding to an ionization potential of 11.96 ev. Vibrational band changes which have been found to accompany the first two members have been assigned to fundamental frequencies of the molecule by comparison with Raman data. The electronic transition, expressed by the Rydberg series, was ascribed to excitation of a &pgr; electron in the triple bond. At higher pressures, a continuous absorption appeared which was followed only to 1600A. No structure could be observed in the spectrum of the ethyl cyanide, although it paralleled that of methyl cyanide in having a stronger absorption starting at 1342A and a weaker one appearing at higher pressures and spreading to longer wave‐lengths.
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