Isomeric yield ratios of 11 fission products were measured in the system of 13 MeV proton-induced fission of232Th by an on-line ion-guide isotope separator. It was found that the closed shell structures of primary fragments and their
complementary fragments affect the isomeric yield ratios. Isomeric yield ratios of121Cd (11/2−, 3/2+) and135Xe (11/2−, 3/2+) were measured precisely in the proton energy range of 13 to 26 MeV to investigate their energy dependence. It was found
that the isomeric yield ratios increased slightly with proton energy. The results were discussed in connection with the deformation
of fission fragments and fission modes.