Beta spectroscopy of some neutron-rich cerium isotopes in252Cf fission products

The method of cyclic-time optimization has been used, in conjunction with a beta-Kx-ray coincidence technique, to obtain the beta spectrum of some decaying cerium isotopes in the fission products of²⁵²Cf. A Kurie plot of the beta spectrum revealed at least four beta groups. From the relative isotopic yields of Kx-ray the isotopic origin of each group has been determined. The coincidence method used in this study allows the measurement of beta groups feeding excited levels of daughter products with high internal conversion coefficients. The end-point energies and isotopic origin of the measured beta groups were as follows: 2.349(±0.100)MeV,¹⁴⁵Ce; 1.715(±0.103)MeV,¹⁴⁵Ce and¹⁴⁸Ce; 1.267 (±0.103)MeV,¹⁴⁵Ce; 0.748(±0.109) MeV,¹⁴⁶Ce and¹⁴⁸Ce.