%0 Journal Article
%A Cederkall, J.
%A Fahlander, C.
%A Golubev, P.
%A Knyazev, A.
%A Iwanicki, J.
%A Wrzosek-Lipska, K.
%A Blazhev, A.
%A Reiter, P.
%A Rosiak, D.
%A Seidlitz, M.
%A Warr, N.
%A Butler, P. A.
%A Gaffney, L. P.
%A Berry, T.
%A Cox, D. M.
%A Pakarinen, J.
%A Kröll, Th.
%A Henrich, C.
%A Schilling, M.
%A Stahl, C.
%A von Schmid, M.
%A Rainovski, G.
%A Berger, C.
%A Berner, C.
%A Gernhäuser, R.
%A Illana, A.
%A De Witte, H.
%A Górska, M.
%A Habermann, T.
%A Saha, S.
%A de Angelis, G.
%A Borge, M. J. G.
%A Tengblad, O.
%A Otsuka, T.
%A Tsunoda, Y.
%T First Measurement of the Quadrupole Moment of the 2<sub>1</sub><sup>+</sup> State in <sup>110</sup>Sn 
%J Physical review letters
%V 135
%N 22
%@ 0031-9007
%C College Park, Md.
%I APS
%M GSI-2026-00246
%P 222502
%D 2025
%Z Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license.
%X The Sn isotopic chain, exhibiting double shell closures at  100 Sn   and  132 Sn  , is a key testing ground for theoretical models of the atomic nucleus. It was originally predicted that the transitional matrix elements between the first 2+ state and the 0+ ground state for the even-even isotopes in this chain should show a simple dependence on the neutron number. This prediction was, however, disproven experimentally in some of the first experiments with postaccelerated radioactive beams, a situation that has remained unresolved ever since. Subsequent theoretical work has suggested that the explanation can be found in proton excitations across the 𝑍 =50 shell gap, with an accompanying experimental signature that the first excited 2+ state in  110 Sn   should have a distinct oblate shape. In this Letter, we present the first measurements of the spectroscopic quadrupole moment of the 2+1 state, 𝐵⁡(𝐸⁢2;4+1→2+1) and 𝐵⁡(𝐸⁢2;4+2→2+1) values for  110 Sn  , as well as the 𝐵⁡(𝐸⁢2;2+1→0+1) value with significantly improved precision compared to previous results. From the same experiment, half-lives of the 2+1 and 4+1 states were measured using the Doppler shift attenuation method. Our combined result, 𝑄⁡(2+1)=20⁢(8)  efm2 for  110 Sn  , is the largest positive value known among the Sn isotopes, indicating an oblate shape of the state by more than 2⁢𝜎. Comparison of the 𝐸⁢2 transition strengths and quadrupole moments with recent shell model calculations are presented.
%F PUB:(DE-HGF)16
%9 Journal Article
%R 10.1103/7ysn-8y1w
%U https://repository.gsi.de/record/364066