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The quasi-particle structures of nuclei in the α-decay chains of 291,293 117 are studied with a modified two-center shell model. The calculated values of Q α are compared with available experimental data. The termination of the α-decay chain of 293 117 is explained.

The one-quasiparticle structures of nuclei in the α-decay chains of 287 114 and 293 116 are studied with a modified two-center shell model. The two-quasiparticle states are revealed in the α-decay chain of even-even nuclei 286,288 114. The calculated values of Q α are compared with available experimental data. The termination of the α-decay chains by spontaneous fission is analyzed.

Abstract. Using the microscopic-macroscopic approach based on the modified two-center shell model, the low-lying quasiparticle spectra, ground-state shell corrections, mass excesses and Q α-values for even Z superheavy nuclei with 108 ≤ Z ≤ 126 are calculated and compared with available experimental data. The predicted properties of superheavy nuclei show that the next doubly magic nucleus beyond 208 Pb is at Z ≥ 120. The perspective of using the actinide-based complete fusion reactions for production of nuclei with Z = 120 is studied for supporting future experiments. Experiments on complete fusion reactions with48 Ca beam and various actinide targets were successfully carried out at FLNR (Dubna), GSI (Darmstadt), and LBNL (Berkeley) in order to synthesize superheavy elements (SHE) with Z = 112-118 [1][2][3][4][5][6][7][8][9][10][11]. The found experimental trend of nuclear properties (Q α -values and half-lives) and cross-sections of production of SHE reveals increasing stability of nuclei approaching the spherical closed neutron shell N = 184, and also indicates a relatively small effect of the proton shell at Z = 114 [3,4,[12][13][14][15] predicted with the microscopic-macroscopic models [16][17][18][19][20][21][22]. This experimental observation seems to be in accordance with the predictions of relativistic and nonrelativistic mean-field models [23][24][25][26] where the island of stability corresponds to Z = 120-126 and N = 184. If there is a strong shell effect at Z = 120-126, then there is hope to synthesize new SHE with Z ≥ 120 by using the present experimental set up and actinide-based reactions with neutron-rich stable projectiles heavier than 48 Ca. With the predictions of the microscopic-macroscopic models [16], where the proton shell at Z = 114 is expected, the reactions 50 Ti+ 249 Cf and 54 Cr+ 248 Cm would result in Z = 120 nuclei with maximum cross-sections of 1.2 and 0.2 fb, respectively, in a 4n evaporation channel [27]. If the predictions of the phenomenological model [28][29][30][31], where the proton shell is assumed at Z = 126, are correct, the reactions 50 Ti+ 249 Cf and 54 Cr+ 248 Cm would lead to the production of Z = 120 nuclei with cross-sections of 550 fb (3n evaporation channel) and 40 fb (4n evaporation channel), respectively [27]. So, the structure of SHE crucially influences the evaporation residue cross-sections in a e-mail: adamian@theor.jinr.ru actinide-based complete fusion reactions. Because nuclear models contain a number of parameters which are fixed for the best description of known nuclei, their predictive power could be smaller for nuclei far from the well-studied region of the nuclear chart. To improve the predictions, one can specially adjust the parameters for describing the known properties of shell-stabilized nuclei close to the region of interest.In refs. [32,33] we proposed a microscopic-macroscopic approach based on the modified two-center shell model (TCSM) [34]. The parameters were set so to describe the spins and parities of the ground state of known heavy nu...

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