The N = 88 ¹⁵⁴Dy rare earth neutron rich nuclei offer an opportunity to study nuclear structure in the transitional region where the nuclear shape changes rapidly from vibrational to rotational motion. The question still remains whether at low spins the N=88 and 90 nuclei structure exhibits permanent octupole deformation [1] or aligned tidal wave octupole phonons [2]. The N = 88 isotones such as ¹⁵⁴Dy₈₈ have remarkable features; they are at a peak in the |M(E3)|² transition strength of 0₁⁺ → 3₁^- transitions for even-even nuclei as a function of neutron number [3]. This experimental evidence is consistent with the interpretation of an octupole vibration. The N = 88 isotones also have very strong E0 transitions from the band built on the 0₂⁺ states to the ground state bands [4,5]. The low spin states of ¹⁵⁴Dy were studied with the AFRODITE spectrometer array equipped with 9 clover High Purity Germanium (HPGe) detectors at iThemba LABS, South Africa. The reaction ¹⁵⁵₆₄Gd₉₁ (³₂He₁, 4n) ¹⁵⁴₆₆Dy₈₈ at 37.5MeV was used to populate these states. A first observation of enhanced E1 transitions in the transitional isotones ¹⁵⁰Sm and ¹⁵²Gd from the levels in the first excited 0⁺ band to the lowest negative parity band has been reported [3]. The results we report here are the first observation of enhanced E1 transitions from the low-lying negative parity band to the band built on the first excited 0⁺ state in ¹⁵⁴Dy. These measurements on ¹⁵⁴Dy extend the systematics on the relationship between the first excited positive parity pairing isomer band and the first excited negative parity band as the nuclear deformation decreases with increasing proton number. Reference [1] R. R. Chasman, Phys. Rev. Lett. 42, 630 (1979). [2] S. Frauendorf, Phys. Rev. C77, 021304(R) (2008). [3] R. H. Spear and W. N. Catford, Phys. Rev. C41, R1351 (1990). [3] S. P. Bvumbi et al., Phys. Rev. C 87, 044333 (2013). [4] A. Passoja et al., J. Phys. G12, 1047 (1986) [5] J. L. Wood et al., Nucl. Phys. A651, 323 (1999)

Choose timezone

53. International Winter Meeting on Nuclear Physics

Support