Pairing-quadrupole interplay in the neutron-deficient tin nuclei: First lifetime measurements of low-lying states in 106,108Sn

M Siciliano,M Siciliano,M Siciliano,M Siciliano,M Siciliano,A Goasduff,A Goasduff,A Goasduff,T Braunroth,M Labiche,G Jaworski,I Kuti,C Michelagnoli,M Zielińska,A Gadea,A Gadea,V González,V González,V González,V González,A Pullia,A Jungclaus,F.J Egea-Canet,I Kuti,B Cederwall,C Müller-Gatermann,U Jakobsson,G De France,G De France,G De France,P Reiter,S Ertürk,D Bazzacco,H Hess,S Leoni,A Maj,R Menegazzo,R Menegazzo,R Menegazzo,R Menegazzo,J Dudouet,D Barrientos,I Kuti,D Testov,J Eberth,P Désesquelles,F Nowacki,F Nowacki,N Cieplicka-Oryńczak,B Birkenbach,B Million,J Nyberg,H Li,D Mengoni,C Fransen,I Kuti,M Doncel,F Recchia,A Lemasson,T Marchi,E Clément,E Clément,E Clément,A Goldkuhle,G Benzoni,T Mijatović,S Szilner,J Collado,D Sohler,M Palacz,Ch Theisen,A P Zuker ,C Domingo‐Pardo ,M D Salsac ,D M Cullen ,A P Zuker ,J J Valiente-Dobón ,Г Георгиев ,Г Георгиев ,Г Георгиев ,Г Георгиев ,A Lefèvre ,E Sanchís ,P R John ,A J Boston ,R M Pérez-Vidal ,W Körten ,W Körten ,А Лопез-Мартенс ,А Лопез-Мартенс ,А Лопез-Мартенс ,А Лопез-Мартенс ,L J Harkness-Brennan ,D S Judson ,D R Napoli ,H C Boston ,O Stézowski ,B Sayğı ,F C L Crespi ,F C L Crespi

doi:10.1016/j.physletb.2020.135474

Abstract

The lifetimes of the low-lying excited states 2+ and 4+ have been directly measured in the neutron-deficient 106,108Sn isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted γ rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the B(E2;21+→0g.s.+) values and it describes well the experimental pattern for 104−114Sn; the B(E2;41+→21+) values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in 108Sn.

Highlights

A little over a decade ago, the Sn isotopes were considered the paradigms of pairing dominance: low-lying states of good seniority, nearly constant J π = 2+1 excitation energies and parabolic B(E2; 2+1 → 0+g.s.) behavior
The emitted γ rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer
Thanks to the precise determination of the ion velocity vector and the identification of the first interaction point of each γ ray inside AGATA, Doppler correction was applied on an eventby-event basis

Summary

Introduction

A little over a decade ago, the Sn isotopes were considered the paradigms of pairing dominance: low-lying states of good seniority, nearly constant J π = 2+1 excitation energies and parabolic B(E2; 2+1 → 0+g.s.) behavior. From Coulomb-excitation measurements with radioactive ion beams only the reduced transition probability between the first excited 2+ state and the ground state could be determined [1,2,3,4,5,6,7,8] Within experimental uncertainties, they suggest a rather-constant behavior for 106 ≤ A ≤ 110, instead of the parabolic trend expected when isovector T = 1 pairing dominates. The B(E2; 4+1 → 2+1 ) values were completely absent in the neutron-deficient Sn isotopes

Results

Discussion

Conclusion