Role of the target orientation angle and orbital angular momentum in the evaporation residue production

Abstract

The influence of the orientation angles of the target nucleus symmetry axis relative to the beam direction on the production of the evaporation residues is investigated for the ${}^{48}$Ca+${}^{154}$Sm reaction as a function of the beam energy. At low energies ($E_{c.m.}<$137 MeV), the yield of evaporation residues is observed only for collisions with small orientation angles ($\hat{I}{\pm }_T<45^0$). At large energies (about $E_{c.m.}=$140--180 MeV) all the orientation angles $\hat{I}{\pm }_T$ can contribute to the evaporation residue cross section $\ddot{I}{ƒ}_{ER}$ in the 10--100 mb range, and at $E_{c.m.}>$180 MeV $\ddot{I}{ƒ}_{ER}$ ranges around 0.1--10 mb because the fission barrier for a compound nucleus decreases by increasing its excitation energy and angular momentum.

20 pages, 10 figures, submitted to JPSJ