EXCITATION-FUNCTION STUDIES FOR DEEP-INELASTIC PROCESSES IN F-19-27 COLLISIONS( AL)

The excitation functions for different fragments produced in the F-19 Al-27 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 fo r different [total kinetic energy loss (TKEL), theta(c.m.)] windows. L arge fluctuations have been observed in all the excitation functions a nalyzed in this work. The Z and angular cross correlation analysis doe s not support a compound nucleus origin of these fluctuations. The coh erence widths extracted from the energy autocorrelation function (EAF) and by the peak counting method do not show, within errors, theta(c.m .), Z, or TKEL dependence. The lifetime of the dinuclear system (DNS) F-19+Al-27 is found to be equal with the DNS's rotation period. This c ould 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. [S0556 -2813(98)00105-8].