Mechanism of the heavy-ion charge exchange reaction 12C(12C,12N)12B at 35 MeV/nucleon.

Abstract

The heavy-ion charge exchange reaction $^{12}$C${(}^{12}$C,$^{12}$N${)}^{12}$ B has been studied at E${(}^{12}$C)=35 MeV/nucleon. Angular distributions in the range 3.7--12.1\ifmmode^\circ\else\textdegree\fi{} (c.m.) have been measured for the ${1}^{+}$ (0.0 MeV), ${2}^{+}$ (0.95 MeV), ${2}^{\mathrm{\ensuremath{-}}}$ (1.67 MeV), and ${4}^{\mathrm{\ensuremath{-}}}$,${2}^{\mathrm{\ensuremath{-}}}$ (4.5 MeV) states in $^{12}$B. A broad peak at 7.8 MeV excitation was also observed. Microscopic one-step distorted-wave Born approximation calculations yield ${V}_{\ensuremath{\sigma}\ensuremath{\tau}}$ strengths \ensuremath{\ge}2 times those obtained in (p,n) reactions at similar energies per nucleon. Although this is significantly smaller than ${V}_{\ensuremath{\sigma}\ensuremath{\tau}}$ values obtained in other heavy-ion charge exchange studies, mostly carried out at energies less than 10 MeV/nucleon, it is concluded that the reaction mechanism is still dominated by sequential transfer (two-step) processes at 35 MeV/nucleon. A rough estimate indicates that one-step processes will dominate at bombarding energies above about 50 MeV/nucleon.