The evidence on single proton energies in the Si isotopes is traced from $N=12$ to $N=28$ using available experimental data on binding energies, single proton transfer reactions, radioactive decay, and direct reaction studies with neutron-rich exotic beams. In addition to demonstrating the value of having information on single particle energies over a long sequence of isotopes, the data point out a significant discrepancy between theoretical and experimental results on the size of the $Z=14$ subshell closure in ${}^{34}\mathrm{Si}$, which is located on the boundary of the island of inversion.

• Received 20 February 2007

DOI:https://doi.org/10.1103/PhysRevC.76.027301