Excitation function studies for deep inelastic processes in19F+27Alcollisions

Abstract

The excitation functions for different fragments produced in the ${}^{19}\mathrm{F}{+}^{27}\mathrm{Al}$ reaction have been measured in the incident energy range 113.5--130.0 MeV in steps of 250 keV. The detection of the outgoing fragments in a large solid angle allowed a study of the excitation functions for different [total kinetic energy loss (TKEL), ${\ensuremath{\vartheta}}_{\mathrm{c}.\mathrm{m}.}$] windows. Large fluctuations have been observed in all the excitation functions analyzed in this work. The $Z$ and angular cross correlation analysis does not support a compound nucleus origin of these fluctuations. The coherence widths extracted from the energy autocorrelation function (EAF) and by the peak counting method do not show, within errors, ${\ensuremath{\vartheta}}_{\mathrm{c}.\mathrm{m}.},$ $Z$, or TKEL dependence. The lifetime of the dinuclear system (DNS) ${}^{19}\mathrm{F}{+}^{27}\mathrm{Al}$ is found to be equal with the DNS's rotation period. This could explain the secondary structures evidenced in the EAF. A reaction mechanism involving the excitation of the DNS in intermediate states of molecular nature is supported by this experimental evidence.