First identification of high-spin states in Ta

Abstract

The yrast band in 166 Ta at high-spin states is established for the first time through the 141 Pr( 28 Si,3n) 166 Ta reaction at a beam energy of 127 MeV. Excitation function, residual radioactivity, and x-γ , γ -γ coincidences were measured. Signature inversion features of 166 Ta and neighbouring isotones are discussed.

Band crossings inTa166

“…Although Ref. [8] suggested that the 148-keV line decaying from the 11 − state is an in-band E2 transition, our normalized angular-correlation ratio of 0.63(6) is consistent with the transition being dipole ( I = 1) in nature. Thus, the 148-keV γ ray presumably feeds an I = 10 level, as drawn in Fig.…”

“…Hild et al [7] investigated the feeding of 166 Ta levels from electron-capture decay of 166 W. A (2) + spin-parity assignment was proposed for the ground state, and four low-spin levels were identified. Zheng et al [8] more recently observed a single rotational band that was assigned to 166 Ta based on x-γ coincidences and on an excitation function. This structure is presented in the level scheme of Fig.…”

“…The tentative spin assignments proposed in Ref. [8] were based upon systematics and were adopted here as well. Band 1 has been extended from I = 24 to 42 as seen in the level scheme ( Fig.…”

“…The odd parity for band 1 was assigned in Ref. [8] based upon the proposed configuration of πh 11/2 νi 13/2 . Because both of these orbitals lie near the Fermi surface, it is logical that they would couple to form the yrast sequence in 166 Ta.…”