Spectroscopy of Rn, Ra and Th isotopes using multi-nucleon transfer reactions

Pear-shaped Nuclei: Nuclear Models and the Standard Model

“…[42,43]) but so far there is little direct information on octupole correlations in these nuclei. The recent measurements of Q 3 values in 220 Rn and 224 Ra are consistent with suggestions from the systematic studies of energy levels [1] that the even-even isotopes 218−222 Rn and 220 Ra have vibrational behaviour while 222−228 Ra have octupole-deformed character. It is concluded [31] that the parity doubling condition that leads to enhancement of the Schiff moment is unlikely to be met in 219,221 Rn.…”

“…These findings should be confirmed by extending studies to other radioactive isotopes in the Rn and Ra chain, and experiments are planned to study 222,228 Ra and 222−226 Rn using HIE-ISOLDE. It is interesting to note that the Gogny HFB calculations [10] predict that Th and U isotopes with N = 134-136, already known to exhibit the characteristics of a rigid octupole shape [1,44], should have significantly enhanced E3 transition strengths (70 Weisskopf units), see figure 3. The predicted yields of these isotopes from the future FRIB facility [45] will in principle be sufficient to measure the transition strengths for isotopes such as 226 Th and 228 U.…”

“…Plots of ∆i x versus ω for nuclei in the Z ≈ 88, N ≈ 134 mass region are given in figures 12 and 13 of Ref. [1]. As can be seen, there are several examples such as 222,224,226,228 Ra and 224,226,228,230 Th where the value of ∆i x tends to zero at low rotational frequencies.…”

“…This condition is met for proton number Z ≈ 34, 56 and 88 and neutron number N ≈ 34, 56, 88 and 134. The largest array of evidence for reflection asymmetry is seen at the values of Z ∼ 88 and N ≈ 134, where phenomena such as interleaved positive-and negative-parity rotational bands in even-even nuclei [1], parity doublets in odd-mass nuclei [2], and enhanced electric-dipole (E1) transition moments [3] have been observed. Many theoretical approaches have been developed to describe the observed experimental features: shell-corrected liquid-drop models [4,5], mean-field approaches using various interactions [6][7][8][9][10], models that assume α-particle clustering in the nucleus [11,12], algebraic models [13] and other semi-phenomenological approaches [14].…”

Studies of pear-shaped nuclei using accelerated radioactive beams

“…The largest array of evidence for reflection asymmetry is seen at the values of Z~88 and N~134, where phenomena such as interleaved positive-and negative-parity rotational bands in even-even nuclei 7 , parity doublets in odd-mass nuclei 8 , and enhanced electric-dipole (E1) transition moments 9 have been observed. Many theoretical approaches have been developed to describe the observed experimental features: shell-corrected liquid-drop models 10,11 , mean-field approaches using various interactions 12,13,14,15,16 , models that assume α-particle clustering in the nucleus 17,18 , algebraic models 19 , and other semi-phenomenological approaches 20 .…”