Entrance channel effects in superheavy element production
Abstract
The difference between evaporation residue cross sections measured in the cold (X+ 208 Pb, 209 Bi) and hot ( 48 Ca+actinides) fusion reactions can be related to the stage of compound nucleus (CN) formation and/or to the stage of its survival against fission. The cold fusion reactions are favorable in synthesis of the superheavy elements (SHE) with charge numbers Z < 112 in comparison with the hot fusion reactions due to small excitation energy and large fission barrier of the CN formed in these reactions. The strong decrease of the cross sections of the synthesis of the SHE Z = 113 in the cold fusion reactions in comparison with the ones in the hot fusion reactions is the result of the increase of hindrance to the CN formation in the cold fusion reactions. The origin of the intrinsic fusion barrier, B * fus , causing the strong decrease of the probability P CN in the cold fusion is discussed.