Fission probability distributions have been measured by ($t,pf$), ($t,\alpha f$), ($t,t^{\prime }f$), ($p,p^{\prime }f$), (${}_{}{}^3{}_{}{}^{}\mathrm{He},df$), and (${}_{}{}^3{}_{}{}^{}\mathrm{He},\alpha f$) reactions with bombarding energies of 15, 16, 20, 22.5, 24, and 24 MeV, respectively. Using targets of ${}_{}{}^{230,232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{231}{}_{}{}^{}\mathrm{Pa}$, ${}_{}{}^{234,236,238}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$, ${}_{}{}^{240,242}{}_{}{}^{}\mathrm{Pu}$, ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}$, and ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ the fission decay of ${}_{}{}^{230,232,234}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{232,236,238,240}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{238,242,244}{}_{}{}^{}\mathrm{Pu}$, and ${}_{}{}^{244,248,250}{}_{}{}^{}\mathrm{Cm}$ was studied. Subbarrier vibrational resonances were observed for ${}_{}{}^{234}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{236,238,240}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$, and ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cm}$. The results are analyzed with a statistical model which involves resonant penetration of the double-humped fission barrier. Estimates of the heights and curvature of the two peaks in the fission barrier are obtained for Th, U, Pu, and Cm isotopes and these values are compared with various theoretical calculations.

[NUCLEAR REACTIONS FISSION measured fission probabilities, $E^{*}\le 7.5$ MeV for ${}_{}{}^{230,232,234}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{232,236,238,240}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{238,242,244}{}_{}{}^{}\mathrm{Pu}$, ${}_{}{}^{244,248,250}{}_{}{}^{}\mathrm{Cm}$ using ($t,pf$), ($t,\alpha f$), ($t,t^{\prime }f$), ($p,p^{\prime }f$), (${}_{}{}^3{}_{}{}^{}\mathrm{He},df$), (${}_{}{}^3{}_{}{}^{}\mathrm{He},\alpha f$) reactions; deduced heights and curvatures for the double-peaked fission barrier for each case.]

• Received 5 December 1973

DOI:https://doi.org/10.1103/PhysRevC.9.1924