[en] Independent isomeric yield ratios of ⁹⁰Rb(1-,4-) and ¹³⁸Cs(3-,6-) in the spontaneous fission of ²⁵²Cf were measured by the radiochemical method. A gas-recoil-transport-system was used for the fast and continuous separation of Rb and Cs from their noble gas precursors Kr and Xe, respectively, in the decay chain. The mean angular momentum of the primary fragments was deduced from the isomeric yield ratios. The results are compared with the results of a previous study. The results indicate that the mean angular momentum of fission fragments is nearly independent of fragment mass. (author)