Low-Ktwo-quasiparticle states in180Ta

Abstract

Excited states in 180 Ta, populated in the 180 Hf(p,n) and (d,2n) reactions, were investigated by in-beam ␥-ray and conversion-electron spectroscopy. In addition to the excited two-quasiparticle bands with K ϭ0 Ϫ and 1 Ϫ known from previous work, we have identified six other low-lying two-quasiparticle bands with K р4. At intermediate K, 12 previously unkown levels were identified that could, however, not be associated reliably with rotational bands. These levels might be of significance in connection with the as yet unresolved problem of the stellar production mechanism for the 9 Ϫ isomer of 180 Ta. At higher K we observe only levels known from the previous in-beam ␥-spectroscopic studies with heavier projectiles, but suggest for some levels a different ordering into rotational bands based on band-mixing considerations. We also report a deuteron spectrum measured in the 181 Ta( p,d) 180 Ta reaction with high resolution and statistics. This spectrum served for configuration assignments and yields an energy of 78Ϯ1 keV for the 9 Ϫ isomer in 180 Ta.

New estimate for the time-dependent thermal nucleosynthesis ofTa180m

“…The isomer ratio is sensitive to the lowest energy of the linkning transitions. Note, however, that available experimental results for this nucleus have found no evidence for direct transitions below 1.09 MeV [20] or 0.739 MeV [25], and that previous γ-ray spectroscopy experiments [15][16][17][18][19] have measured no semi-direct transitions lower than 1.09 MeV; this fact indicates that the lowest energy of the linking transitions is the known energy of 1.09 MeV. We choose, therefore, P m /(P g +P m ) = 0.39 based only on the observed 9 linking transitions for the following discussion.…”

“…If one knew sufficient information on transitions between the two states of 180 Ta, the branching ratio could be calculated by the mathematical method of [14]. However, although many experiments have been carried out to identify the paths between the two states in 180 Ta [15][16][17][18][19], such paths have never been identified and only transition probaiblities have been measured [8,20]. In this letter, therefore, we develop a new calculation method which can be applied even with limited information.…”

Signature splitting in two quasiparticle rotational bands of 180,182Ta

“…(2) To test the role of Newby shift energy for the above-mentioned shifting of odd spin members with respect to even spin members.…”

“…The most prominent aspect of this nuclide is the concern with K π = 9 − : 9/2 − [514] π ⊗9/2 + [624] ν isomeric state lying at 78.0 keV energy [2,3]. This isomeric state lives more than 1.2×10 15 yr [4,5] which is much large as compared to the K π = 1 + : 7/2 + [404] π ⊗9/2 + [624] ν ground state whose half-life is only 8.18 h [6,7].…”