N15(He3,d)O16Reaction and Structure of Oxygen-16

Abstract

The structure of ${\mathrm{O}}^{16}$ has been studied by means of the ${\mathrm{N}}^{15}({\mathrm{He}}^3,d){\mathrm{O}}^{16}$ reaction. The experiments were performed with 16.00- and 24.90-MeV ${\mathrm{He}}^3$ beams from the tandem Van de Graaff accelerator at Rochester. Reaction products were analyzed and recorded automatically by means of a high-resolution magnetic spectrometer equipped with a sonic-spark counter connected to an on-line computer system. In the region of excitation up to about 22 MeV, 14 lines have been identified with levels of ${\mathrm{O}}^{16}$, all having odd parity except the ground state (which was strongly excited), the first excited state (which was weakly excited), and the third excited state (which was barely detectable). Many well-known states were not seen. The experimental data have been analyzed by use of distorted-wave Born-approximation (stripping theory) calculations, and the results have been compared with expectations from wave functions of the shell model and of the "mixed model" exemplified in the work of Brown and Green and of Kelson. The strengths of the transitions are mostly found to be in good agreement with predictions of the mixed model and, where applicable, the shell model, although the $J=2^{-}$, $T=0\mathrm{}$ state at 12.53 MeV seems somewhat too strongly excited. However, a strongly excited state tentatively identified as a $J^{\pi }=3^{-}$, $T=0\mathrm{}$ state of ${\mathrm{O}}^{16}$ lying at 13.12 MeV is not predicted by any of the theories used in the comparisons.