A 25 MeV/nucleon primary ${}^{17}\mathrm{O}$ beam was used to produce an isomeric state ${}^{18}{\mathrm{F}}^m$ beam via the single-nucleon transfer reaction ${}^{17}\mathrm{O}$ ${(}^{12}\mathrm{C},$ ${}^{11}\mathrm{B})$${}^{18}{\mathrm{F}}^m.$ The total nuclear reaction cross section, ${\sigma }_R,$ of ${}^{18}{\mathrm{F}}^m$ (metastable) on silicon was measured using a stack of silicon surface barrier detectors that included a position sensitive silicon detector (PSD). The total reaction cross sections were determined as a function of bombarding energy up to 400 MeV by measuring the energy loss in each detector. The reaction cross sections were measured both for a mixture of metastable- and ground-state ions and for a pure ground-state beam. The reaction cross sections for ${}^{14}\mathrm{N}$ and ${}^{16}\mathrm{O}$ beams were also measured simultaneously. The reaction cross sections for the metastable beam were deduced from the mixed- and the ground-state cross sections, corrected for the measured purity of the mixed-state beam. The observed reaction cross sections for ${}^{18}{\mathrm{F}}^m$ are larger at low energies than the cross sections measured for the ground state. The isomeric cross sections can be reproduced by an optical model potential having a diffuseness of 0.8 fm, compared to a more conventional diffuseness parameter of 0.5 fm, which is adequate to reproduce the ${}^{14}\mathrm{N},$ ${}^{16}\mathrm{O},$ and ${}^{18}{\mathrm{F}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ cross sections measured in this experiment.

• Received 1 October 2001

DOI:https://doi.org/10.1103/PhysRevC.65.044605