Heavy particle residues arising from the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ entrance channels have been mass identified with a time-of-flight system for boron projectile energies from 14 to 54 MeV in one MeV intervals. Both entrance channels cover a ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ excitation energy range from approximately 25 to 50 MeV. With the exception of decays to the mass 15 and 18 residues, the decay of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ system to a particular mass is similar in magnitude and energy dependence to the decay of the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ system to that mass. This similarity in the two systems and the differences in the mass 15 and 18 decays can be explained in terms of the entrance channel angular momenta and the available decay channels. In addition to the individual decay cross sections, the total ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ fusion cross sections have been measured. Both entrance channels show evidence of a fusion cross section limitation. These limitations cannot presently be explained in terms of a critical compound nucleus level density.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$,$X$), $14\le E_{\mathrm{lab}}\le 54$ MeV; ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $E_{\mathrm{lab}}=25, 40, \mathrm{and} 50$ MeV; ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$,$X$), $14\le E_{\mathrm{lab}}\le 48$ MeV; ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$)${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, $E_{\mathrm{lab}}=18, 25, 32, 39, \mathrm{and} 46$ MeV; measured $\frac{d^2\sigma }{d\Omega }\mathrm{dE}$ for reaction products $M=9-22\mathrm{}$; deduced critical and grazing angular momenta.

• Received 13 November 1981

DOI:https://doi.org/10.1103/PhysRevC.25.2963