(3He, d) and (α, t) reaction studies of 154Gd: nature of Kπ=4+ bands in heavy deformed nuclei

Levels in 154Gd have been studied with (3He,d) and (α,t) reactions using beams of 24 MeV 3He and 27 MeV α particles. Particle spectra were measured with a magnetic spectrograph at θ=30° and 60° for the (3He,d) and at θ=45° and 60° for the (α,t) reaction. Cross sections were compared with predictions based on Distorted Wave Born Approximation and Nilsson model calculations. The γ-vibrational band has an admixture of ∼15% of the 5/2+[413]−1/2+[411] two-quasiproton state, in good agreement with predictions of the Quasiparticle-Phonon Model. The Kπ=4+ band at 1646 keV is very strongly populated, with a pattern of cross sections indicating its dominant component is an ∼80% admixture of the 5/2+[413]+3/2+[411] two-quasiproton state. Bands with similar structures have previously been found at 1510 keV in 156Gd and 1380 keV in 158Gd. Although there were earlier double-γ-phonon claims for the bands in 154Gd and 156Gd, quantitative analyses show that all the data (including the E2 strengths) agree better with a predominantly g boson, or single hexadecapole phonon, character. Some insights are provided which assist in understanding how microscopic structures of the Kπ=4+ and γ bands help produce the relatively large E2 strengths coupling these bands. Two closely-spaced Kπ=1+ bands based at 2175 keV and 2186 keV share the single-proton stripping strengths for the 5/2+[413]−3/2+[411] configuration, and a level at 2569 keV is proposed as the 7− member of a Coriolis-mixed band formed by transfer of a proton to h11/2 orbitals.