Photochemicalreaction of the 2-vinylnaphthalene (VN)-fumaronitrile (FN) system by direct irradiation, which proceeds probably via ion radicals generated by electron transfer in the excited singlet state of VN to yield a VN-FN copolymer and VN cyclodimers, contrasts with the benzophenone-sensitized reaction, which proceeds via the triplet states of VN and FN with no dominant contribution of electron