Octupole vibrational states in the even-mass barium isotopes

A low-lying state of sup(132,134,136,138)Ba, strongly excited in the scattering of 20 MeV α-particles at 1750, is identified as the first 3- octupole vibrational state in each case. Angular distribution measurements for α-particle scattering to this state and the well-known first 2+ state in sup(132,134,136,138)Ba are in agreement with harmonic-vibration coupled-channel predictions. Deformation parameters are obtained, and the deduced isoscalar transition rates are compared with measured electromagnetic transition rates. The first 3- states of sup(132,134,136,138)Ba are found to be at excitation energies of 2.070, 2.251, 2.529 and 2.879 MeV, respectively. A state in 130Ba at an excitation energy of 1.948 MeV is tentatively identified as the first octupole-vibrational state in this nucleus. (orig.)