Identification of a new heavy neutron-rich isotope Th-238

A new heavy neutron-rich thorium isotope was produced via a multinucleon tr ansfer reaction by irradiation of natural uranium targets with 60 MeV/u O-1 8 ions. The Th activities was radiochemically separated from the uranium an d mixture of reaction products by the rapid solvent extraction method. Meas urements of the gamma-ray spectra were performed with HPGe detectors. The n ew neutron-rich isotope Th-238 was identified for the first time based on t he observation of the growth and decay of the gamma-ray with energy of 1060 .5 keV from the decay of Pa-238. The half-life of Th-238 has been determine d to be 9.4+/-2.0 minutes. Further, a gamma-ray of 89.0 keV with the 8.9-mi nute half-life was found, which may be due to the decay of the new isotope Th-238.