The reaction cross sections of ${}^{27,28}\mathrm{P}$ and the corresponding isotones on Si target were measured at intermediate energies. The measured reaction cross sections of the $N=12$ and 13 isotones show an abrupt increase at $Z=15$. The experimental results for the isotones with $Z⩽14$ as well as ${}^{28}\mathrm{P}$ can be well described by the modified Glauber theory of the optical limit approach. The enhancement of the reaction cross section for ${}^{28}\mathrm{P}$ could be explained in the modified Glauber theory with an enlarged core. Theoretical analysis with the modified Glauber theory of the optical limit and few-body approaches underpredicted the experimental data of ${}^{27}\mathrm{P}$. Our theoretical analysis shows that an enlarged core together with proton halo are probably the mechanism responsible for the enhancement of the cross sections for the reaction of ${}^{27}\mathrm{P}+{}^{28}\mathrm{Si}$.

• Received 26 June 2003

DOI:https://doi.org/10.1103/PhysRevC.69.034326