GAMMA-RAY MULTIPLICITY STUDIES FOR AR-40 AND KR-86 INDUCED REACTIONS LEADING TO ER-COMPOUND NUCLEI AT LIMITING ANGULAR MOMENTA

The moments of the γ-ray multiplicity distributions as a function of evaporation residue and of Eγ have been determined from γ-multiplicity measurements for the 116, 120, 122, 124Sn(40Ar, xn) reactions at 161 ≦ E(Ar) ≦ 236 MeV and for the 76Ge(86Kr, xn) reaction at 314 ≦ E(Kr) ≦ 376 MeV. Even at the highest incident energies where lgr ≈ 120 units, it is not possible to populate nuclei with l > 65 units, the limiting l predicted for a rotating liquid drop. For the lowest incident energies these data are in agreement with the decay of a compound system. At the highest incident energy, however, significant deviations are observed from the expected decay of an equilibrated system. Such deviations are indicative of pre-equilibrium particle decay. Statistical calculations utilizing the code GROG12 are used to substantiate these conclusions. No evidence for a lower l-cut in the population of the compound system is observed; however, these data would not be sensitive to an lcut ≲ 10 units. The moments of inertia extracted from the edge of the collective E2 bump" in the 〈Mγ〉 versus Eγ data are in agreement with those predicted for a rotating liquid drop. The average multiplicity of the noncompound processes is estimated to be 8-11 for lgr ≲ 100 units and increasing to 21 for lgr ≲ 120 units. © 1979."