Abstract
The ground-state bands of the neutron-rich Th-236 and U-242 nuclei were established up to spin 10 and 8, respectively, by in-beam gamma-ray spectroscopy using the (O-18, Ne-20) two-proton pickup reaction with a U-238 and a Pu-244 target. Deexcitation gamma rays in Th-236 and U-242 were identified by selecting the kinetic energies of Ne-20 using Si Delta E-E detectors. The excitation energies of the first 2(+) states in U and Pu isotopes have local minima at N similar or equal to 146, suggesting the possibility that nuclei with Z similar or equal to 92 have a spherical shell closure of N=164. Calculation using the Koura-Yamada single-particle potential gives an energy gap of 1.8 MeV at N=164 for U-256.