Speaker
Description
I will report on the first γ-ray spectroscopy of $^{51,53}$K produced from $^{52,54}$Ca(p,2p) reactions at ~250 MeV/nucleon at RIBF at RIKEN. The 1/2$_{1}^{+}$ →3/2$_{1}^{+}$ transitions in $^{51,53}$K were clearly observed [1], providing important information to understand the monopole drift effect of the proton 1d$_{3/2}$ and 2s$_{1/2}$ orbitals along the odd-K isotopic chain. Thanks to the MINOS setup based on reaction vertex tracking combined with a thick-hydrogen target [2], the final-state angular-momentum of $^{51,53}$K were determined unambiguously by comparing the shapes of the experimental exclusive parallel momentum distributions to distorted-wave impulse approximation calculations. 3/2+ ground states and 1/2+ first excited states in $^{51,53}$K were established quantifying the natural ordering of the 1d$_{3/2}$ and 2s$_{1/2}$ proton-hole states that are restored at N = 32 and 34. State-of-the-art ab initio calculations and shell-model calculations with improved phenomenological effective interactions reproduce the present data and predict consistently the increase of the E(1/2$_{1}^{+}$) - E(3/2$_{1}^{+}$) energy differences towards N = 40.
[1] Y. L. Sun et al., Phys. Lett. B 802, 135215 (2020).
[2] A. Obertelli et al., Eur. Phys. J. A 50, 8 (2014).
