Single-photon ionization of the clusters C2F4 . O-2, (C2F4)(2)O-2, (C2F4)(2), and (C2F4)(3) is reported for energies up to 25 eV. The ionization potentials found are IP(C2F4 . O-2)=9.879+/-0.01 1 eV, IP([C2F4](2)O-2)=9.776+/-0.016 eV, IP([C2F4](2))=9.826+/-0.017 eV, and IP([C2F4](3))=9.838+/-0.022 eV. In addition, we measured IP(C2F4)=10.117+/-0.004 eV, in excellent agreement with Drier work. The appearance potential of C2F4+ from C2F4 . O-2 was found to be AP=10.253+/-0.012 eV, which, when combined with appropriate values from above gives the cluster dissociation energies D-0(C2F4 . O-2)=0.136+/-0.013 eV (3.14+/-0.29 kcal mol(-1)), and D-0([C2F4 . O-2](+))=0.374+/-0.016 eV (8.62+/-0.38 kcal mol(-1)). The former value helps to understand the remarkable solubility of oxygen in fluorocarbons. No evidence was seen for photoionization-induced reactions of O-2 with C2F4. A surprisingly intense Rydberg progression converging to the excited state of C2F4+ near 16.0 eV can be identified in the parent C2F4, and persists strongly in all four of the clusters studied. The lack of oxygen-containing reaction products and the persistence of the Rydberg state convey information about the structure of C2F4 . O-2.