Evidence for shape coexistence in 52Cr through conversion-electron and pair-conversion spectroscopy
Department of Nuclear Physics, Research School of Physics, Australian National University, Canberra ACT 2601, Australia
2 Research Center for Nuclear Physics (RCNP), 10-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan
3 School of Physics, University of the Witwatersrand, Johannesburg, 2000, South Africa
4 Department of Physics, Faculty of science, Stellenbosch University, Private Bag X1, Matieland 7602, Cape Town, South Africa
5 Department of Subatomic Physics, iThemba LABS, Old Faure Road, Somerset West 7129, P.O. Box 722, Cape Town, South Africa
* e-mail: email@example.com
** Present Address: Department of Physics, University of Oslo, N-0316 Oslo, Norway
Published online: 6 April 2020
Electric monopole (E0) transitions are a highly sensitive probe of the charge distribution of an atomic nucleus. A large E0 transition strength (ρ2(E0)) is a clear indicator of nuclear shape coexistence. In the region between doubly magic 40Ca and 56Ni, E0 transitions have never been observed in the Ti or Cr isotopes, nor in the heavier iron isotopes (56,58Fe). We have performed the first measurements of the E0 transitions in 52Cr via conversion-electron and pair-conversion spectroscopy using the Super-e spectrometer at the Australian National University Heavy Ion Accelerator Facility. We present the first spectra obtained for 52Cr, including the first observation of the E0 transition from the first-excited 0+ state in 52Cr, in both electron-positron pairs and conversion-electron spectroscopy. The preliminary values for the E0 strength in the 1531keV 2+ → 2+ transition in 52Cr is ρ2(E0) × 103 = 470(190), and for the 1728-keV 23+ → 21+ transition, it is ρ2(E0) 103 = 1800(1200). The large E0 strengths observed are consistent with shape coexistence in this region. However, despite the relatively precise observation of the conversion-electron and electron-positron pair intensities, the E0 strengths have large uncertainties. More precise determinations of relevant spectroscopic quantities, such as the state lifetimes and transition mixing ratios for mixed M1 + E2 transitions, are needed to determine the E0 strength more precisely.
© The Authors, published by EDP Sciences, 2020
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