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The tungsten isotopes exist in a region of deformed nuclei with soft, triaxial shapes that evolve into oblate deformation as the proton, Z, and (or) neutron, N, numbers increase, before reaching sphericity at $Z = 82$ [1]. The heaviest stable W ($Z = 74$) isotope is at $A=186$. Its low-lying structure has been investigated in the past using Coulomb excitation [2] and $\beta$ decay [3]; however, experimental data on the non-yrast, higher-spin states are sparse due to their inaccessibility through any suitable heavy-ion fusion-evaporation reactions. In this work, non-yrast, excited states in neutron-rich $^{186}$W were populated via inelastic-scattering reactions using stable beams of $^{136}$Xe nuclei accelerated to 725 and 800 MeV (10 and 20% above the Coulomb barrier) [4]. Scattered ions were detected in CHICO2, and de-exciting γ rays in Gammasphere. Considerable progress was made in extending the $K^π = 2^+$ (γ), $K^π = 0^+$ and $K^π = 2^-$ (octupole) bands. A staggering pattern observed in the energies of levels in the $K^π = 2^+$ band was found to be consistent with a potential that gets softer to vibration in the γ degree of freedom with increasing spin. The odd-even staggering of states in the $K^π = 2^-$ band was found to exhibit a phase opposite to that seen in the γ band. This effect is most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in $^{186}$W.
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Grants No.~DE-FG02-94ER40848 (UML), No.~DE-FG02-97ER41041 (UNC), No. DE-FG02-97ER41033 (TUNL) and DE-FG02-94-ER40834 (UMCP), and Contracts No.~DE-AC02-06CH11357 (ANL) and No.~DE-AC52-07NA27344 (LLNL), the International Technology Center Pacific (ITC-PAC) under Contract No.~FA520919PA138 (ANU), and the National Science Foundation. The research used resources of ANL's ATLAS facility, which is a DOE Office of Science user facility.
- K. Kumar and M. Baranger, Nucl. Phys. A 110, 529 (1968).
- F. K. McGowan $et~al$., Nucl. Phys. A 289, 253 (1977); W. T. Milner $et~al$., Nucl. Phys. A 177, 1 (1971); R. Kulessa, $et~al$., Phys. Lett. B 218, 421 (1989).
- E. Monnand $et~al$., Nucl. Phys. A 134, 321 (1969).
- V. S. Prasher, PhD thesis (2015).
