Interaction and fusion of deformed nuclei
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CLEI Theory
Interaction and Fusion of Deformed Nuclei V. Yu. Denisov* and N. A. Pilipenko Institute for Nuclear Research, National Academy of Sciences of Ukraine, pr. Nauki 47, 03680, Kyiv, Ukraine Received July 24, 2009; in final form, December 9, 2009
Abstract—It is shown that the height of the barrier and its position, as well the depth of the capture well, are highly sensitive to the relative orientation of colliding strongly deformed nuclei. It is found that the fusion/capture cross sections and the nucleus–nucleus potential for heavy nuclear systems depend greatly on the magnitude and sign of the quadrupole deformation of nuclear surfaces. In order to describe correctly the cross section for the capture of heavy strongly deformed nuclei, it is necessary to perform averaging over all three angles that describe their relative orientation. Allowance for a hexadecapole deformation leads to a significant increase in the capture cross section for very heavy nucleus–nucleus systems. DOI: 10.1134/S1063778810070082
1. INTRODUCTION The fusion of nuclei is widely used in nuclear physics to produce nuclei far off the beta-stability line and superheavy nuclei, to explore the properties of excited nuclear states and the mechanisms of their decay, and to study the dynamics of nuclear reactions [1–6]. The burning of stars is also associated with reactions involving the subbarrier fusion of nuclei [7]. Nuclei studied thus far are mostly deformed. Deformed nuclei are frequently used in experimentally studying various nuclear reactions and are involved in nuclear reactions proceeding in stars [8]. Therefore, investigation of reactions between deformed nuclei at energies in the vicinity of the barrier is of great topical interest. In studying in detail subbarrier-fusion reactions, the respective cross sections were found to exceed considerably the predictions of the model of onedimensional tunneling. Various models and mechanisms of fusion reactions were proposed for describing a considerable enhancement of the cross section at subbarrier energies (see [5, 6, 8–22] and references therein). The orientation of deformed nuclei affects significantly the barrier height [9, 13, 14, 17, 22–25] and the shape of the capture well in the nucleus–nucleus potential [25]. By way of example, we indicate that, in reactions between the spherical nucleus 48 Ca and the deformed heavy nuclei 238 U, 244 Pu, and 248 Cm— one employs these reactions to produce superheavy nuclei [26]—the change in the barrier height in response to changes in orientation may be as large as some 20 MeV [24]. Variations in the barrier height for *
different orientations of two deformed heavy nuclei are still greater [25]. The cross section for the fusion of nuclei at energies in the vicinity of the barrier depends greatly on the barrier height; therefore, orientation effects are of importance for correctly calculating the cross section for the fusion of deformed nuclei. Our study reported in [25] was devoted to studying in detail and calculating the potential of the interactio
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