Speaker
Description
Configuration mixing and quantum phase transitions in odd-mass nuclei around $^{100}$Zr
J.-M. Régis$^1$, A. Pfeil$^1$, J. Jolie$^1$, A. Esmaylzadeh$^1$, L. Knafla$^1$, M. Ley$^1$, U. Köster$^2$, Y. H. Kim$^2$, N. Gavrielov$^3$ and K. Nomura$^4$
1: IKP, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
2: ILL, 71 avenue des Martyrs CS 20156, 38042 Grenoble Ceknomura@phy.hrdex 9, France
3: Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520-8120, USA
4: Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb, Croatia
Abstract
Several N = 60 isotones around $^{100}$Zr show rotational structures based on a deformed ground state. The shape transition from spherical single-particle structures of the N = 50 closed-shell isotones to quadrupole deformation at N = 60 can be described in terms of Quantum Phase Transitions (QPT). Recently, calculations using the Interacting Boson Model with configuration mixing (IBM-CM) of the ground and the 2p-2h intruder states could very well describe the experimentally observed sudden (sharp) shape transition in the even-Zr isotopes going from N = 58 to N = 60 as an abrupt configuration crossing (type II QPT) [1]. The calculation revealed that the type II QPT is accompanied by a type I QPT of the intruder state as gradual spherical-to-deformed shape transition of this configuration [1]. The calculations have been extended to the odd-Nb isotopes with N = 52-64 using the IBFM-CM by coupling the $\pi$(1g$_{9/2}$) orbit to the Zr boson core [2]. Similarly to the even-Zr isotopic chain, the odd-Nb disclose a Type II QPT at N = 60 accompanied by a type I QPT of the intruder configuration and which is the feature of an intertwined QPT [1,2].
We are reporting on further investigation on QPTs by presenting results of $\gamma$-$\gamma$ lifetime measurements of the lowest excited states in the odd $^{99}$Zr and $^{99}$Nb nuclei. Highly effective and precise $\gamma$-$\gamma$ fast-timing experiments have been performed at the LOHENGRIN fission-fragment separator of the Institut Laue-Langevin [3]. The deduced transition rates are compared with newest calculations on $^{99}$Nb within the IBFM-CM framework. Experimental results of transition rates in $^{99}$Zr [3] have been used to investigate QPTs by comparing with the IBFM constructed with deformation constrained self-consistent mean-field calculations based on the relativistic Hartree-Bogoliubov model with a choice of a universal energy density functional and pairing interaction [4].
[1] N. Gavrielov, A. Leviatan and F. Iachello, Phys. Rev. C 105 (2022) 014305
[2] N. Gavrielov, A. Leviatan and F. Iachello, Phys. Rev. C 106 (2022) L051304
[3] A. Pfeil, Master Thesis, Universität zu Köln 2022
[4] K. Nomura, T. Niksic and D. Vretenar, Phys. Rev. C 102 (2020) 034315
