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

A complete set of existing data on hot fusion reactions leading to synthesis of superheavy nuclei of Z = 114-118, obtained in a series of experiments in Dubna and later in GSI Darmstadt and LBNL Berkeley, was analyzed in terms of an angular-momentum-dependent version of the fusion-by-diffusion (FBD) model with fission barriers and ground-state masses taken from the Warsaw macroscopic-microscopic model (involving nonaxial shapes) of Kowal et al. The only empirically adjustable parameter of the model, the injection-point distance (s(inj)), has been determined individually for all the reactions. Very regular systematics of this parameter have been established. The regularity of the obtained s(inj) systematics indirectly points at the internal consistency of the whole set of fission barriers used in the calculations. (In an attempt to fit the same set of data by using the alternative theoretical fission barriers of Moller et al. we did not obtain such a consistent result.) Having fitted all the experimental excitation functions for elements Z = 114-118, the FBD model was used to predict cross sections for synthesis of elements Z = 119 and 120. Regarding prospects to produce the new element Z = 119, our calculations prefer the Es-252(Ca-48,xn)(300-x) 119 reaction, for which the synthesis cross section of about 0.2 pb in 4n channel at E-c.m. approximate to 220 MeV is expected. The most favorable reaction to synthesize the element Z = 120 turns out to be Cf-249(Ti-50,xn)(299-x) 120, but the predicted cross section for this reaction is only 6 fb (for 3n and 4n channels).