A New Heavy Neutron-rich Isotope 238Th

A new nuclide ²³⁸Th has been produced via multinucleon transfer reaction induced by 60MeV/u ¹⁸O ion irradiation of natural uranium. The thorium was radiochemically separated from the mixture of uranium and its reaction products. The activity of thorium was measured by using a HPGe detector and a planar HPGe detector. The ²³⁸Th has been identified for the first time by measuring the growth and decay of the γ-rays from its daughter ²³⁸Pa. The half-life of 238Th was determined to be (9.4±2.0)min. In addition,a new (89.0±0.3)keV γ-ray with T_1/2=(8.9±1.5)min was observed and assigned to ²³⁸Th decay based on the measurement of transition energy and half life.