Speaker
Description
The development of collectivity along the N = Z is one of the subjects that has recently attracted great experimental efforts. In particular, heavy N = Z nuclei in the mass region A = 80 are expected to be some of the most deformed ground states which have been found [1] in mid-mass nuclei, typically 8p−8h, 12p−12h for e.g. the cases of $^{76}$Sr, $^{80}$Zr. This strong enhancement of collectivity with respect to lighter N=Z nuclei has its origin in cross shell excitations across the N=40 shell gap to g9/2, d5/2 and s1/2 which are intruder quadrupole partners generating deformations. These structures can be interpreted in terms of algebraic Nilsson-SU3 self-consistent model to describe the intruder relative evolution in the vicinity of $^{80}$Zr[2]. In this presentation, we will expose some of the latest developments in microscopic nuclear structure calculations for exotic nuclei far from stabilitity at the N=Z line[3]. The new theoretical calculations for the very region of $^{80}$Zr will be presented for the first time within the interacting shell model framework using an enlarged model space outside a $^{56}$Ni core comprising the pseudo-SU3 p3/2 f5/2 p1/2 and quasi-SU3 g9/2 d5/2 s1/2 orbitals for both protons and neutrons. We will present and compare results from both exact Shell Model diagonalization [4] and our newly developed DNO Shell Model approach employing beyond mean field techniques[5,6].
These theoretical calculations allow a very good description of the rapid transition (A = 60 − 100) from spherical to deformed structures which can be intepreted in terms of “simple” many particles - many holes configurations. The whole Island of Collectivity in the region defines an Island of Inversion for proton-rich nuclei and the sudden shape change recently observed between $^{84}$Mo and $^{86}$Mo-$^{88}$Ru is interpreted as an effect on the N=50 gap induced by the addition of the two neutrons, a fingerprint of three-body forces[7,8].
[1] R. D. O. Llewellyn et al., Phys. Rev. Lett. 124, 152501 (2020).
[2] A. P. Zuker et al., Phys. Rev. C 92, 024320 (2015)
[3] D. D. Dao, F. Nowacki, A. Poves in preparation
[4] E. Caurier, G. Martínez-Pinedo, F. Nowacki, A. Poves, and A. P. Zuker, Rev. Mod. Phys. 77, 427 (2005)
[5] D. D. Dao and F. Nowacki, Phys. Rev. C 105, 054314 (2022)
[6] D. D. Dao and F. Nowacki, EPJ Web Conf. 342, 01009 (2025)
[7] J. Ha et al., Nature Communications 16, 10631 (2025)
[8] M. Bentley et al., submitted to Physical Review