Influence of neutron-core excitations on high-spin states in 88 Sr

High-spin states of the nucleus ${}^{88}\mathrm{Sr}$ have been studied via the reaction ${}^{80}\mathrm{Se}{(}^{11}\mathrm{B},p2n)$ at a beam energy of 45 MeV. Gamma rays were detected with the six-detector array OSIRIS CUBE. The level scheme of ${}^{88}\mathrm{Sr}$ has been extended up to $E\ensuremath{\approx}11 \mathrm{MeV}$ and $J=17.$ Mean lifetimes of three levels have been determined using the Doppler-shift-attenuation method. The level structures in ${}^{88}\mathrm{Sr}$ have been interpreted in terms of the shell model. The calculations were performed in the configuration space ${(0f}_{5/2}{,1p}_{3/2}{,1p}_{1/2}{,0g}_{9/2})$ for the protons and ${(1p}_{1/2}{,0g}_{9/2}{,1d}_{5/2})$ for the neutrons. These calculations describe the high-spin level sequences linked by $M1$ transitions with strengths of $B(M1)\ensuremath{\approx}0.3$ to 1.4 W.u. as multiplets of seniority $\ensuremath{\upsilon}=4$ and 6 states including proton configurations and neutron-core excitations.