Analysis of Excitation Functions inCm(C,xn)NoReactions

Excitation functions for the synthesis of ${}_{}{}^{251}{}_{}{}^{}\mathrm{No}$, ${}_{}{}^{252}{}_{}{}^{}\mathrm{No}$, ${}_{}{}^{253}{}_{}{}^{}\mathrm{No}$, ${}_{}{}^{254}{}_{}{}^{}\mathrm{No}$, ${}_{}{}^{255}{}_{}{}^{}\mathrm{No}$, ${}_{}{}^{256}{}_{}{}^{}\mathrm{No}$, and ${}_{}{}^{257}{}_{}{}^{}\mathrm{No}$ in the bombardments of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Cm}$, ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}$, and ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ are presented. A good fit to these functions has been obtained by the use of the Jackson formula as modified to include fission and angular-momentum effects. Experimental values of ${〈\frac{{\Gamma }_n}{{\Gamma }_f}〉}_{\mathrm{av}}$ are compared with the semiempirical formula of Fujimoto and Yamaguchi and the following new empirical formula: ${log}_{10}\left(\frac{{\Gamma }_n}{{\Gamma }_f}\right)=-0.276Z+f\left(N\right)\mathrm{}$, where $f\left(N\right)\mathrm{}$ is $5.46+0.140N$ for $N\leqq 153$ and $19.23+0.050N$ for $N\geqq 153$. A brief discussion of $\frac{{\Gamma }_n}{{\Gamma }_f}$ systematics of transberkelium nuclides and the effect of the 152-neutron subshell is given.