Isotopic yields of intermediate-mass fragments emitted in E/A=50 MeV 4He+116,124Sn reactions

Inclusive yields of isotopically resolved intermediate-mass fragments (IMF) with Z=3--6 have been measured for the reaction of E/A=50 MeV 4He with 116Sn and 124Sn targets. The isotopic yield patterns reflect the N/Z ratio of the target for both equilibriumlike and nonequilibrium components of the spectra. In addition, the IMF elemental cross sections for the 124Sn target decrease much more rapidly with Z than for 116Sn. This effect is presumably due to lower barriers for IMF emission from residues formed with the neutron-deficient 116Sn target and increased competition from pre-IMF neutron emission for the neutron-excess 124Sn target. The experimental cross sections are compared with statistical and accreting-source calculations