The independent fractional chain yields of Y90, Nb96, and La140 have been measured from fission of Th232 with alpha particles. The excitation energy was varied from about 20 to 40 MeV. Yields are also calculated for Cs136 from data previously published. In addition, the independent fractional chain yields of Y92, Nb96, and La140 were measured from fission of U235 with 14.9-MeV neutrons. From these data, smoothly varying plots of independent yield versus excitation energy were constructed for Y90, Nb96, Cs136, and La140. The data from 14.9-MeV neutron fission of U235 are in good agreement with those from alpha-particle fission of Th232 at the same excitation energy. It is shown that, within the limits of certain assumptions regarding the charge dispersion curves, the shift in Zp (the most probable charge for a given mass number) with increasing excitation energy varies among the nuclides studied. In particular, it appears that dZpdE may be significantly greater for heavy fragments than for light fragments. The data for Y90, Nb96, and La140 are consistent with linear plots of Zp versus E*, except that the value for Nb96 for thermal-neutron fission of U235 is off the curve by 0.1 charge unit. The value of dZpdE for Cs136 decreases with energy in this energy range, possibly because of shell effects at low excitation energies.