Spectroscopic study of Th228-234 nuclei using multi-nucleon transfer reactions

Light-actinide nuclei in the octupole deformed region have been populated u sing multi-nucleon transfer from Th-232. The energy level schemes of severa l thorium isotopes with A = 228-234 have been extended up to I similar to 2 4 (h) over bar and negative parity states have been observed for the first time in Th-234. A systematic study of the difference in alignment between t he positive- and negative-parity bands in thorium nuclei in this mass regio n shows that Th-228,Th-230,Th-234 behave like octupole vibrators, in contra st with Th-224,Th-226, which are octupole-deformed in character. An intrins ic electric dipole moment has been measured for the first time in Th-234. T he small value obtained is consistent with the vibrational description of t his nucleus.