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

Abstract

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 a new angular-momentum dependent version of the fusionby-diffusion (FBD) model with fission barriers and ground-state masses taken from the Warsaw macroscopic-microscopic model (involving non-axial shapes) of Kowal et al. The only empirically adjustable parameter of the model, the injection-point distance (sinj), has been determined individually for all the reactions. Very regular systematics of this parameter have been established. The regularity of the obtained sinj 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 Möller 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 252 Es( 48 Ca,xn) 300−x 119 reaction, for which the synthesis cross section of about 0.2 pb in 4n channel at Ec.m. ≈ 220 MeV is expected. The most favorable reaction to synthesize the element Z = 120 turns out to be 249 Cf( 50 Ti,xn) 299−x 120, but the predicted cross section for this reaction is only 6 fb (for 3n and 4n channels).

Experimental studies of the249Bk + 48Ca reaction including decay properties and excitation function for isotopes of element 117, and discovery of the new isotopeOganessian1, Abdullin2, Alexander3 et al. 2013Phys. Rev. C1347480View full textAdd to dashboardCite

“…Also shown in Fig. 4 are calculated cross sections for the 3n to 5n evaporation channels of the 249 Bk+ 48 Ca reaction within a model based on multidimensional Langevin-type dynamical equations [15] and the fusion-by-diffusion model [16]. The calculated cross sections are in good agreement with results of experiment.…”

“…Some other models predict comparable cross-section values but the energies of the maxima of the xn evaporation channels are predicted to be somewhat lower (see, e.g., [17,18]) than those measured in this experiment. [15] and dashed [16] lines.…”

Qαvalues in superheavy nuclei from the deformed Woods-Saxon model

“…One of the likely reactions leading to this element seems to be 48 Ca( 252 Es,3n) 300−x 119 see eg. [48]. Note, that this α-particle chain contains the known decay chain of 293 117 [21].…”

Investigation of the48Ca + 249–252Cf reactions synthesizing isotopes of the superheavy element 118

“…[7,8]), we presented results of calculation on the abovementioned reactions which could lead to the Z=120 superheavy element, but we found values of the evaporation residue cross sections lower than 0.1 pb. Predictions of other authors are approximately near this value [9][10][11][12][13]. Therefore, it is necessary to improve the experimental conditions in order to be able to reach measurements of cross sections of the order of fb.…”