Predictions of the fusion-by-diffusion model for the synthesis cross sections of Z = 114–120 elements based on macroscopic-microscopic fission barriers

摘要

A complete set of existing data on hot fusion reactions leading to synthesis of superheavy nuclei ofnZ = 114–118, obtained in a series of experiments in Dubna and later in GSI Darmstadt and LBNL Berkeley,nwas analyzed in terms of an angular-momentum-dependent version of the fusion-by-diffusion (FBD) modelnwith fission barriers and ground-state masses taken from theWarsaw macroscopic-microscopic model (involvingnnonaxial shapes) of Kowal et al. The only empirically adjustable parameter of the model, the injection-pointndistance (sinj), has been determined individually for all the reactions. Very regular systematics of this parameternhave been established. The regularity of the obtained sinj systematics indirectly points at the internal consistencynof the whole set of fission barriers used in the calculations. (In an attempt to fit the same set of data by using thenalternative theoretical fission barriers of M¨oller et al. we did not obtain such a consistent result.) Having fitted allnthe experimental excitation functions for elements Z = 114–118, the FBD model was used to predict cross sectionsnfor synthesis of elements Z = 119 and 120. Regarding prospects to produce the new element Z = 119, ourncalculations prefer the 252Es(48Ca,xn)300−x119 reaction, for which the synthesis cross section of about 0.2 pb in 4nnchannel at Ec.m. ≈ 220 MeV is expected. The most favorable reaction to synthesize the element Z =120 turns outnto be 249Cf(50Ti,xn)299−x120, but the predicted cross section for this reaction is only 6 fb (for 3n and 4n channels).