In-beam spectroscopy of thek π=0? bands in230–236U

TheK ^π=0^? bands in even uranium nuclei were studied in the compound reactions²³¹Pa(p, 2n)²³⁰U,^{230, 232}Th(α,2n)^{232, 234}U and²³⁶U(d, pn)²³⁶U. In-beamγ-rays were measured in coincidence with conversion-electrons, which were detected with an iron-free orange spectrometer. The negative-parity levels are observed up to intermediate spins (I<13^?). In addition, the 1^? and 3^? levels in²³⁰U were confirmed by a decay study with an isotope separated²³⁰Pa source. For the heavier isotopes (A≥232) the properties of theK ^π=0^? bands (energies andγ-branchings) are consistent with a vibrational character of these bands. For²³⁰U theK ^π=0^? band lies at rather low energy (E(1^?)=367 keV), and the level spacings within this band are very similar to those of the isotones²²⁸Th and²²⁶Ra, which might indicate the onset of a stable octupole deformation.