We recorded the IR spectra of C2H4+ trapped in solid Ar through electron bombardment of a mixture of ethylene and Ar during matrix deposition. The four most intense lines of C2H4+ were observed and assigned according to comparison with the literature data for ethylene with solid Ne and the predicted vibrational anharmonic wavenumbers. Experiments involving further UV irradiations of the matrix samples were performed in the region 345-225 nm. Upon UV radiation, lines of C2H4+ decreased and lines corresponding to C2H4, C2H2, and C2H3 increased, indicating that the photodissociation and photoassisted neutralization of C2H4+ in the matrix may occur simultaneously. (C) 2015 Elsevier B.V. All rights reserved.