Isospin Mixing in the Isobaric Analog State Derived from the (p,nIASp̃) Reaction on140Ce,172,174,176Yb, and208Pb

Abstract

An exclusive coincidence experiment using the $({p,n}_{\mathrm{IAS}}\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{p})$ reaction on ${}^{140}\mathrm{Ce}$, ${}^{172,174,176}\mathrm{Yb}$, and ${}^{208}\mathrm{Pb}$ was carried out for the first time by measuring decay protons from the isobaric analog states (IAS). Spreading widths of the IAS are deduced from the escape and total widths. The results show a strong isospin dependence which can be explained by the isospin mixing effect due to the coupling to the ${T}_{0}$ component among three multiplets ${T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}T}_{0}\ensuremath{-}1$, ${T}_{0}$, and ${T}_{0}+1$ of isovector monopole states in daughter nuclei. Empirical isospin mixing probabilities are found to be consistent with microscopic sum rule predictions.