Solid-state reactions of F atoms with ethene molecules were initiated by UV photolysis of dilute solutions of F-2 and C2H4 in solid Ar. Products stabilized in the matrix were detected by infrared spectroscopy. Experiments were conducted at different temperatures in order to distinguish reactions in matrix-isolated F-2-C2H4 complexes (at 16 K) from reactions of diffusing thermal F atoms (at 26 K). Comparison with the kinetic EPR data (Benderskii, V. A. et al. Mendeleev Commun. 1995, 6, 245) permitted the identification of the infrared spectrum of the beta-fluoroethyl radical, which is the main product of the F + C2H4 reaction. Frequencies and absolute absorption intensities of the eight strongest infrared bands of beta-C2H4F are reported. Photolysis of isolated F-2-C2H4 complexes forms the closed-shell products C2H3F-HF and trans- and gauche-1,2-C2H4F2 with relative yields 0.6:0.2:0.2. Successive addition of two thermal F atoms to an isolated C2H4 molecule forms only the two conformers of 1,2-C2H4F2. The difference between product branching ratios of the latter reaction and the direct photoinduced reaction of F-2-C2H4 complexes is qualitatively explained by the difference in size of the reaction cages and excess energies of the vibrationally excited intermediate (C2H4F2)*.