Positive- and negative-parity yrast bands in the transitional nucleide 150Sm and the interacting boson approximation

The 150Nd(α, 4n) reaction at Eα = 45 MeV has been used to study high spin states in the 15062Sm 88 nucleide. The experiments comprised measurements of singles γ-ray and conversion electron spectra, γ-ray angular distributions, three-parameter ( Eα- Eα- t) coincidences and a γ-ray anti-Compton spectrum. Predominantly populated were the ground-state band (g.s.b.) extending to Jπ = 12 + and tentatively to 16 + and a negative-parity odd spin band (n.p.b.) extending from Jπ = 5 - through 15 - and tentatively to 19 -. The bands are interpreted in the framework of the interacting boson approximation model with a Hamiltonian appropriate for a transitional nucleus, far away from either the rotational or vibrational limit. It is found that the model gives a very satisfactory description of the energies of the two bands observed as well as of the branching ratios of the intra- and inter-band transitions. The gentle backbending of the {2ℷ}/{h̷}2 versus (ħω) 2 curve for g.s.b. above Jπ = 10 + is reproduced in the calculation without making use of the band-crossing concept. The absolute reaction cross sections have been determined at 45 MeV bombarding energy to be σtot = 1380 ± 170 mb and σ4n = 800 ± 100 mb.