An energy shift between the fusion barrier and interaction barrier in heavy nuclear systems

Autor: A.G. Demin, Yu. Ts. Oganessian, I. V. Shirokovsky, E. A. Cherepanov, S.P. Tretyakova, V. K. Utyonkov, A.S. Iljinov
Rok vydání: 1989
Předmět:
Zdroj: Il Nuovo Cimento A. 101:225-240
ISSN: 1826-9869
0369-3546
DOI: 10.1007/bf02813994
Popis: The mass asymmetry influence upon the extra energy ΔB=Bfus−Bint has been investigated in nuclear systems withZi+Zt≥100. This was achieved by the experimental measurement of the production cross-sections for244Fm and several nuclides withZ=104÷108 via complete fusion reactions with bombarding ions ranging from50Ti to76Ge. The method has been developed to derive the ΔB values from the maximum cross-sections of the «cross-reactions» (HI; 1n, 2n). The empirical ΔB values derived in the present work are compared with liquid-drop model predictions. The latter model appears to explain only qualitatively the onset of the dynamical hindrance to the fusion process in heavy systems, which leads to the extra energy ΔB over the interaction barrier required for the system to reach fusion. This result agrees with the data analysis carried out in other works and indicates, probably, a significant influence of nuclear structural effects upon «cold fusion» dynamics and on the ΔB values. Although nuclear structural effects favour the use of Pb-like targets for «cold fusion», a steep increase in the empirical ΔB values for heavier systems sets the limit for the «cold» synthesis method atZ=110. In addition, an analysis involving more detailed (though fragmentary) data on (HI, 1n, 2n) excitation functions shown not only an extra energy increase but also a monotonic enhancement of sub-barrier fusion for the heavier systems like HI+Pb. The data on highly fissionable heavy systems, obtained in the present work, serve as a test for the currently developed theoretical models of the nuclear fusion process.
Databáze: OpenAIRE
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