Studying fusion reactions for effect of P(CN) on heavy nucleus formation and for nuclear structure effects.

摘要

The fusion reaction 208Pb (50Ti, xn) 258-xRf (x = 1-3) was studied to determine PCN (probability that the mononucleus system evolves to form a compound nucleus inside the fission saddle point) and to establish the value of Wsur (survival probability) for the given reaction experimentally. The fission excitation function was measured at five beam energies. Angular distributions were fit using the Back et al. prescription to determine JCN and sigma CN. The total fission cross section (sigmafis) and compound nucleus cross section (sigmaCN) at each of the energies were used for calculating PCN. These experimentally determined values of PCN and sigmafis and the values of sigma EVR determined in previous studies of this system were used in the equation sigmaEVR = sigmac x PCN x Wsur to arrive at Wsur for each of the energies. The experimental value of W sur for 1n channel agrees very well with the one based on theoretical predictions of Moller et al. The subsequent lowering in Wsur with beam energy is attributed to onset of 2n and 3n evaporation channels.; The fusion reaction 9Li+70Zn was studied to determine the effects of nuclear structure of the projectile (neutron skin) on fusion. The fusion excitation function was measured at seven near- and sub-barrier beam energies. Radioactivity in the irradiated target was measured by gamma-spectroscopy and in radiochemically separated EVRs by beta-spectroscopy. The 9Li fusion radius determined by fitting the excitation function with Wong formula was 12.1 +/- 1.0fm, much larger than 2.5fm given by R0 xA1/3. This extension of the radius is attributed to the presence of spatially extended neutron skin. The excitation function also showed a large sub-barrier fusion enhancement not explained by standard coupled channel model. An attempt was made at measuring the fusion excitation function with 11Li projectile (neutron halo nucleus) which would enable us to do a comparative study as 9 Li is the core of 11Li halo nucleus but it failed due to low beam intensity.