Speaker
Description
Shape coexistence is a phenomenon where multiple shapes occur within the same nucleus and has been proposed to exist in all nuclei [1]. In particular, neutron-deficient Pb nuclei near the N=104 mid-shell provide fruitful ground for investigating this phenomenon. Notably, $^{186}$Pb, $^{188}$Pb and $^{190}$Pb isotopes exhibit three distinct shapes near their ground states [2-7]. In the shell-model picture, these three shapes are associated with 0p-0h (spherical), 2p-2h (oblate) and 4p-4h (prolate) multiproton-multihole configuration [8].
Recently, we have performed two complementary in-beam experiments to asses competing shapes in the $^{190}$Pb nucleus: one utilised a simultaneous in-beam γ-ray and conversion electron spectrometry, and the other employed plunger device for lifetime measurements of excited states. These experiments allowed for the reassigning of the yrast band with a predominantly oblate shape, confirmed predominantly prolate shape assignment for the non-yrast band, and discovered a candidate for the spherical 2$^+$ state. These findings highlight the power of combining these two distinct methods to enhance our understanding on shape coexistence.
This presentation will cover the latest in-beam experiments in this region performed at the Accelerator Laboratory in Jyväskylä, Finland [3,6,7].
[1] Heyde, K. & Wood, J. L. Phys. Scr. 91, 083008 (2016)
[2] Andreyev, A. N. et al. Nature 405, 430–433 (2000)
[3] Ojala, J. et al. Commun. Phys. 5, 213 (2022)
[4] Bijnens, N. et al. Z. Phys. A, 356, 1 (1999)
[5] Dracoulis, G. et al. Phys. Rev C, 69, 054318 (2004)
[6] Montes-Plaza, A. et al. Comm.phys. 8, 8 (2025)
[7] Papadakis, P. et al. Phys. Lett. B 858, 139048 (2024)
[8] Heyde, K. & Wood, J. L. Rev. Mod. Phys. 83, 1467–1521 (2011).
