Enhanced E1 deexcitations in 218Ra and the evolution of reflection asymmetry at moderate spins

High-spin octupole yrast levels inRn21686

“…The B(E1)/B(E2) ratio for the transitions 19 − −→ 18 + and 19 − −→ 17 − is an order of magnitude smaller than the B(E1)/B(E2) ratios observed for the transitions from negative to positive parity states up to the 17 − state. Values as small as this reduced value have also been observed in the heavier isotopes 218,220 Rn[22].The average value B(E1)/B(E2) = 3.2 × 10 −7 fm −2 found in 216 Rn, turns out to be 7.4 times smaller than the average value for 218 Ra, 2.3 × 10 −6 fm −2[23] and 5.6 times…”

Isoscalar dipole transition as a probe for asymmetric clustering

“…The 1 − cluster states with the α + 14 C configuration in 18 O were experimentally searched by using the E1 strength as a probe [43,44], in addition to the ordinary experimental methods such as α scattering and breakup [45][46][47][48]. The α clustering in the actinides [49][50][51] were also investigated in the same literature. Recently, the α clustering in 212 Po [52][53][54] and the rare-earth nuclei [55] were also discussed based on their enhanced low-lying E1 strengths.…”

Identification of theJπ=1−state inRa218populated viaαParr1, Smith2, Greenlees3 et al. 2016Phys. Rev. C60101View full textAdd to dashboardCite

“…The ground state of 218 Ra is expected to be spherical [8], but it has been shown that at high spins, the yrast states form an alternating-parity sequence, with enhanced E1 transitions between the positive-and negative-parity states [9][10][11][12][13]. This high-spin structure is characteristic of strong octupole correlations, and it has been suggested that the octupole shape in this nucleus is stabilised by rotation [12,14]. The low-lying negative-parity states in 218 Ra, specifically, those with J π = 1 − and 3 − , can thus offer valuable insight into the development of octupole collectivity in this region as a function of N , and also as a function of angular momentum.…”