Argonne National Laboratory

Reference | Abstract | Physics

Electric monopole transitions to probe shape coexistence in atomic nuclei

Heavy Ion Discussion Group, May 10, 2023, 3:30 pm CDT

Host: Filip Kondev

Electric monopole transitions to probe shape coexistence in atomic nuclei *

Tibor Kibédi

 Department of Nuclear Physics and Accelerator Applications

Australian National University, Canberra, ACT Australia

Electric monopole, E0 transitions are unique to nuclei; they are not observed in any other manifestations of matter [1]. The reason for this ‘‘isolated’’ manifestation is because photons have spin one, and nuclei are well isolated from their environment by atomic electrons. Thus, electromagnetic decay by single-photon emission is forbidden for a transition between two states with spin zero. However, decay is possible through the interaction between the nucleus and its atomic electrons: the so-called internal conversion process. While the formation region of higher multipole order transitions (E1, M1, E2, etc.) is dominantly outside the nucleus, the formation region of E0 transitions, involving a different set of nuclear matrix elements, takes place inside the nuclear volume. Decay is also possible through the creation of electron–positron pairs (if the decay energy exceeds the mass of the pair, i.e., ΔE > 1.022 MeV): the so-called internal pair formation (IPF). E0 transitions – in competition with M1 and E2 multipole orders – are also possible between two states with the same parity and J>0 states.

In this talk we will report on selected results on E0 transitions in 12C [2,3], 40Ca [4] and in the fp shell nuclei around N=28, using the Super-e for conversion electron and electron-positron pair spectroscopy.

We will also examine the possibility to use high resolution pair spectroscopy to search for the X17 particle.

  1. T. Kibédi, A.B. Garnsworthy and J.L. Wood, Prog. in Part. and Nucl. Phys. 123 (2022) 103930
  2. T. Kibédi, et al., Phys. Rev. Lett. 125, 1(2020) 82701
  3. T.K. Eriksen, et al., Phys. Rec. C 102 (2020) 024320
  4. E. Ideguchi, et al., Phys. Rev. Lett. 128 (2022) 252501.

* Project supported by the Australian Research Council - DP140102986 and DP170101673