Identification Of A New Heavy Neutron-Rich Isotope Th-238

A new heavy neutron-rich thorium isotope was produced via a multinucleon transfer reaction by irradiation of natural uranium targets with 60 MeV/u O-18 ions. The Th activities was radiochemically separated from the uranium and mixture of reaction products by the rapid solvent extraction method. Measurements of the gamma-ray spectra were performed with HPGe detectors. The new neutron-rich isotope Th-238 was identified for the first time based on the 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 determined to be 9.4+/-2.0 minutes. Further, a gamma-ray of 89.0 keV with the 8.9-minute half-life was found, which may be due to the decay of the new isotope Th-238.