Nuclear reaction in extreme condition is one of the attractive topics from the point of view of not only the nuclear structure and reaction but also the nucleosynthesis. Although the electron capture rate in supernova explosion is estimated from the charge exchange reaction with the ground state, the charge exchange reaction with the high-excitation energy state may provide the rate in the similar circumstance with the supernova explosion. Fusion reactions with superdeformed nuclei may provide us the high spin limit.
In some nuclei, there are long-lived states with high spins, so called isomers. The 12+ state in 52Fe is a typical high-spin isomer with the lifetime of 46 second. The production of such an isomer beam provides us the opportunities to challenge the reactions with high-temperature and high-spin state. Presently the reported isomer ratio of 52Fe(12+) is below 1% while the isomer ratio of 10% is required for charge exchange reactions. In this study we are aiming at the production of high-isomer-ratio beams by changing the transfer momentum and incident angle.
Experiment (program number H362) was performed at HIMAC in Chiba. The ratios of isomeric states in the beams are measured by using projectile fragmentation from 58Ni and 82Kr, changing momentum transfer, incident angle and incident nucleus.The incident energy was 350 MeV/u, which is similar to the typical incident energy at RIBF. The beam particles implanted the active stopper of plastic scintillator and two germanium detectors were placed beside the stopper in order to measure the gamma rays from the decay of isomeric states. The decay gamma ray from isomer of 52Fe was clearly observed and typical isomer ratio is more than 10 %.
In this talk, we report the detail of experiment and its result, and discuss the isomer production via fragmentation reactions.