Angular Momentum Limits in Fusion Reactions Induced by Argon and Krypton Projectiles

Evaporation residue cross sections from the fusion of52Cr+110Pd

“…The relevant information for the decay of the compound nucleus and calculated cross sections are assembled in Table 2. A constant fission barrier reduction factor of f=0.6 as function of incident energy which is not in agreement with our results, would also be in contradiction with results of [4] and [12] where at the highest energies a maximum population up to 65 h is found for almost the same compound system with mass A = 162 in different fusion reactions using varying mass asymmetry in the entrance channel.…”

“…5 for a fission barrier reduction factor f=0.6 corresponds to a limiting Lvalue (a=~2~2L2 of Lm=47 ). This value is, however, too small to be compatible with the limiting angular momentum of ~ 65 h found in other fusion reactions leading to a similar compound mass [12]. We find that the fission competition in the compound nucleus decay leading to the measured evaporation residue cross sections is only correctly reproduced with a fission barrier lowered to 70-80 % of the RLD value.…”

Particle-to-fission competition at high excitation energies

“…Similar conclusions have been drawn in [10]. Very large evaporation and fission product cross sections [6,[33][34][35][36][37][38][39], where the sharpcutoff entrance channel/-value for fusion exceeds the value /max beyond which RLDM theory [11] predicts a vanishing fission barrier and infinitely short lifetimes of the intermediate composite nuclei, can thus be understood. Following the above argument, some enhancement of very heavy element production cross section is to be expected, as compared to classical statistical model predictions.…”

Fusion Reactions Between Heavy Nuclei

“…Fission competition is usually included in evaporation calculations with an angular-momentum-dependent, fission barrier height given by the rotating liquid drop model (RLDM) (203). Although the magnitude of the fission barrier height predicted by the RLDM may be too high (194,204), the application of the statistical model, including fission competition, to evaporation residue data (103,122,127,139,151,170,197,(205)(206)(207) and direct examination of angular momentum limits to evaporation residue production (27,33,35,36,54,140) confirm that the fission barrier height declines with increasing angular momentum and reaches zero close to the angular momentum limit predicted by the RLDM (208,209). The RLDM predicts that, as the mass of the nucleus increases, the angular momentum that the nucleus may stably sustain in the absence of fission rises to a peak value of about 90 at a mass of about 120 and then begins to decline to zero at a mass of about 310.…”