Weak interaction rates in16Oand18O

Abstract

The weak interaction rates in ${}^{16,18}\mathrm{O}$ are investigated in detail in a large shell-model space. Special attention is given to the muon capture process, which populates the states in ${}^{16,18}\mathrm{N}.$ The best agreement with experimental rate is obtained when unquenched weak-coupling constants are used. The roles of different multipoles are discussed, along with their strength distributions. The extracted mean excitation energy in muon capture is 10.6 MeV in ${}^{16}\mathrm{O}$ and 9.9 MeV in ${}^{18}\mathrm{O},$ close to the dipole resonance. The isotope effect is also discussed.