Shell-model configuration-interaction description of quadrupole collectivity in Te isotopes

Abstract

We present systematic calculations on the spectroscopy and transition properties of even-even Te isotopes by using the large-scale configuration interaction shell model approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behavior, which cannot be reproduced by collective models. Our calculations reproduce well the equallyspaced spectra of those isotopes as well as the constant behavior of the B(E2) values in 114 Te. The calculated B(E2) values for neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The B(E2) of light isotopes can exhibit a nearly constant bevavior upto high spins. We show that this is related to the enhanced neutron-proton correlation when approaching N = 50. [13][14][15][16][17][18][19][20][21] activities, in particular regarding the fundamental roles played by core excitations and the nuclear pairing correlation (or seniority coupling). The study of transition rates in isotopic chains just above Z = 50 may provide further information on the role of core excitations [22,23]. The limited number of valence protons and neutrons are not expected to induce any significant quadrupole correlation in this region [24][25][26][27]. The low-lying collective excitations of those nuclei were discussed in terms of quadrupole vibrations [24,28] in relation to the fact that the even-even Te isotopes between N = 56 and 70 show regular equallyspaced yrast spectra (c.f., Fig. 1 in Ref. [24]). If that is the case, the Te isotopes will provide an ideal ground to explore the nature of the elusive nuclear vibration and the residual interactions that leading to that collectivity. However, the available E2 transition strengths along the yrast line in 114,120−124 Te show an anomalous rotationallike behavior, which can not be reproduced by collective models or the interacting boson model [29,30]. Another intriguing phenomenon is the nearly constant behavior of the energies of the 2 + and 4 + states in Te and Xe isotopes and their ratios when approaching N = 50, in contrast to the decreasing behavior when approaching N = 82 [24]. This was analyzed in Ref.[31] based on the quasiparticle random phase approximation approach where an competition between the quadurople-quadrupole correlation and neutron-proton pairing correlation was suggested.An enhanced interplay between neutrons and protons * chongq@kth.se is expected in the 100 Sn region since the protons and neutrons partially occupy the same quantum orbitals near the Fermi level [24,[31][32][33]. In relation to that, there has also been a long effort searching for superallowed alpha decays from those N ∼ Z isotopes [34,35]. The region is also expected to be the endpoint of the astrophysical rapid proton capture (rp) process [36,37]. The octupole correlation may also play a role here (the coupling between the 0h 11/2 and 1d 5/2 orbitals) [26,38,39]. Still, compa...

High-spin structure in the transitional nucleus Xe131 : Competitive neutron and proton alignment in the vicinity of the N=82 shell closure

“…The calculation was performed with the program KSHELL. It was shown that the calculations reproduce well the excitation energies and E2 transition probabilities in even-even Te isotopes [89,90]. 131 Xe.…”

Millisecond 23/2+ isomers in the N=79 isotones Xe133Kaya1, Vogt2, Reiter3 et al. 2018Phys. Rev. C5070View full textAdd to dashboardCite

“…A renormalization was performed by a perturbative G matrix approach to include core-polarization effects. It was shown that the calculations reproduce well the excitation energies and E2 transition probabilities in even-even Te isotopes [64,65].…”

“…In 129 Sn the seniority v = 3 multiplet is completed by the J π = (27/2 − ) state at E x = 2552 keV [T 1/2 = 0.27 (7) μs], identified by Lozeva et al in 2008 [4]. 131 Te was populated in a pioneering 64 Ni + 130 Te multinucleon-transfer experiment at the GASP γ -ray spectrometer [10]. A delayed 361-564-833-keV triple-γ coincidence was identified to form the (21/2 − ) → (19/2 − ) → (15/2 − ) → 11/2 − yrast band.…”

To Shell Model, or Not to Shell Model, That Is the Question

“…Moving to heavier nuclei, the effective charges in the 132 Sn region are near the default values [62], although most recent calculations adopt e p ≈ 1.7e and e n ≈ 0.8e [32,34,63,64]. The measured B(E2) for 130 Sn [46,47] is lower than theory and the experimental systematics (see [65]); the experiment should be repeated.…”