Quasifission and fusion-fission in reactions with massive nuclei: Comparison of reactions leading to the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Z</mml:mi><mml:mo>=</mml:mo><mml:mn>120</mml:mn></mml:mrow></mml:math>element
Аннотация
The yields of evaporation residues, fusion-fission, and quasifission fragments in the $^{48}\mathrm{Ca}+^{144,154}\mathrm{Sm}$ and $^{16}\mathrm{O}+^{186}\mathrm{W}$ reactions are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues for the $^{48}\mathrm{Ca}+^{154}\mathrm{Sm}$ reaction can be well reproduced. The measured yields of fission fragments are decomposed into contributions coming from fusion-fission, quasifission, and fast-fission. The decrease in the measured yield of quasifission fragments in $^{48}\mathrm{Ca}+^{154}\mathrm{Sm}$ at the large collision energies and the lack of quasifission fragments in the $^{48}\mathrm{Ca}+^{144}\mathrm{Sm}$ reaction are explained by the overlap in mass angle distributions of the quasifission and fusion-fission fragments. The investigation of the optimal conditions for the synthesis of the new element $Z=120$ $(A=302)$ show that the $^{54}\mathrm{Cr}+^{248}\mathrm{Cm}$ reaction is preferable in comparison with the $^{58}\mathrm{Fe}+^{244}\mathrm{Pu}$ and $^{64}\mathrm{Ni}+^{238}\mathrm{U}$ reactions because the excitation function of the evaporation residues of the former reaction is some orders of magnitude larger than that for the last two reactions.