Half-life of the yrast2+state in188W: Evolution of deformation and collectivity in neutron-rich tungsten isotopes

Abstract

The half-life of the yrast I π = 2 + state in the neutron-rich nucleus 188 W has been measured using fast-timing techniques with the HPGe and LaBr 3 :Ce array at the National Institute of Physics and Nuclear Engineering, Bucharest. The resulting value of t 1/2 = 0.87(12) ns is equivalent to a reduced transition probability of B(E2; 2 + 1 → 0 + 1 ) = 85(12) W.u. for this transition. The B(E2; 2 + 1 → 0 + 1 ) is compared to neighboring tungsten isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES) calculations have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly increasing γ softness for [184][185][186][187][188][189][190][191][192] W and an oblate minimum for 194 W.

Heavy rotation – evolution of quadrupole collectivity centred at the neutron-rich doubly mid-shell nucleus 170Dy

“…While the E(2 + ) and R(4/2) observables were discussed here, for a complete picture the B(E2) values have a strong dependency on the evolution of collectivity. Such information can be obtained with the ROSPHERE array [32,33] that has previously been used successfully in this region [34], or with a fast timing campaign using AGATA at GANIL [35].…”

Prompt Response Function (PRF) of Lifetime Measurement in the 2+ State of 192Os Nuclei Energy Levels from Triple-Gamma Coincidence Techniques

“…Apart from the fact that these techniques are classified based on the range of lifetime information associated with the energy levels, convolution and the centroid shift methods can widely be employed in the measurement of these lifetimes of the nuclear levels [10,11,12,13,14,15]. In these approaches, two or more γ ray transitions are used; the populating transition(s) to an energy level and the depopulating transition(s) out of the energy levels [2]; bringing about the gamma coincidence techniques.…”

“…In this method, the desired decay path/cascade can be selected with the use of a high-resolution Ge detector. More recently [13,14,15,18,19], the use of triple coincidences for lifetime measurements in the picosecond region has been developed, where the time difference, ∆T, is obtained between the coincident cerium-doped LaBr 3 scitillators gated with a HPGe energy coincidence [20,21]. This has led to an improvement compared to the previous BaF 2 based analysis due to the superior energy resolution and fast decay time for LaBr 3 (Ce) detectors [22,23].…”

Shapes, softness, and nonyrast collectivity in W186

“…Figure 1 presents some key systematic trends in the tungsten isotopes between 176 ≤ A ≤ 188 [7][8][9][10][11][12][13]. Energy systematics [18], as well as known B(E2; 2 + 1 → 0 + 1 ) values [19,20], indicate that 186 W, at N = 112, lies beyond the maximum axial deformation and is softening in shape [4].…”