[Formula Presented]-decays of neutron-deficient americium isotopes

Neutron-deficient americium isotopes [Formula Presented] were produced in the bombardment of multiple thin targets of [Formula Presented] and [Formula Presented] with [Formula Presented] ions. The reaction products were effectively mass-separated using the on-line isotope separator (JAERI-ISOL) coupled to a helium gas-jet transport system. For the first time, the [Formula Presented] transition of [Formula Presented] was observed, and some improved [Formula Presented]-decay data for [Formula Presented] and [Formula Presented] ([Formula Presented]-decay daughter of [Formula Presented]) were accumulated. The [Formula Presented]-particle energies of [Formula Presented] and [Formula Presented] were determined to be [Formula Presented] and [Formula Presented] and their half-lives were [Formula Presented] and [Formula Presented], respectively. Measured [Formula Presented]-decay branching ratios of [Formula Presented] and [Formula Presented] were [Formula Presented] and [Formula Presented], respectively, while the lower limit for [Formula Presented]-decay of [Formula Presented] was deduced to be [Formula Presented]. Hindrance factors and probable assignments of the levels involved in those [Formula Presented] transitions are discussed.