How to observe hyperdeformed states populated in heavy ion and induced fission reactions

A possibility to consider highly deformed states in heavy nuclei as the dinuclear system (DNS)-type configuration was demonstrated in some papers. In literature the formation of the HD states are usually treated in the fusion-fission mechanism. In this paper the optimal conditions in heavy-ion and induced fission reactions for the population of long living cold DNS are determined which are related to the high- and low-spin HD states or to nuclear molecular resonances. The potential energy of the dinuclear system is expressed as the function of the internuclear distance and the charge and mass asymmetry coordinates as well as the angular momentum quantum number L. The semi-phenomenological potential is calculated on this model. Due to the density dependent nucleon-nucleon interaction, the nuclear part of the potential is attractive for larger internuclear distances and repulsive for smaller distances. In between the potential has a pocket as a function of the internuclear distance with small depth due to the predominance of the attractive nuclear force over the Coulomb and the centrifugal forces. The quasibound states in the pocket are interpreted as the HD states. The depth of the pocket decreases with angular momentum L and vanishes for L > 100 in the systems considered here. Considering the population of the highly deformed states in heavy ion reactions, following three conditions are supplied to obtain long survival of the DNS in the quasibound states. 1) Formed DNS must be cold. 2) The DNS should be formed with energy of the quasibound state lower than the barrier height around the minimum in the charge asymmetry coordinate direction. 3) Spherical and stiff nuclei (magic or double magic) are favorable. Optimal experimental conditions to find HD states in some heavy ion reactions are presented. The population of highly deformed states in induced fission is considered. It is proposed as a new experimental method to measure the rotational gamma-quanta in coincidence with decay fragments of the DNS to identify the high-spin HD state directly. A method of identification of the low-spin HD isomers by measuring the decay fragments of the isomeric DNS at the energies of transmission resonance in sub-barrier induced fission is suggested. (S. Funahashi)