https://doi.org/10.1140/epja/s10050-022-00755-1
Regular Article - Experimental Physics
Multiparticle-hole excitations in nuclei near N = Z = 20: 
K
1
Department of Physics, Florida State University, 32306, Tallahassee, FL, USA
2
Physics Division, Oak Ridge National Laboratory, 37831, Oak Ridge, TN, USA
Received:
28
January
2022
Accepted:
26
May
2022
Published online:
15
June
2022
This experimental study of high-spin structure near 
nuclei was focused on K, but will also mention three newly observed 
transitions in Ca observed in the same reaction. High-spin states were populated using the 
Mg(
O, 
)K and Mg(O, 
)Ca reactions. The experiment was carried out at an incident beam energy of 50 MeV at the Florida State University (FSU) John D. Fox Superconducting Linear Accelerator Laboratory and used the FSU high-purity germanium detector array. The K level scheme was extended to 12325 keV, possibly with J
= 25/2
or 27/2
, by means of 25 new transitions and that of Ca to 9916 keV. Linear polarization and a measure of angular distribution results are also reported and used to provide information on the spins and parities of several states in the K level scheme. The results have been compared to the spsdpf cross-shell FSU shell model interaction calculations. The theoretical results from configurations involving no or one additional nucleon promoted from the sd to the fp shell agree relatively well with the energies of known states, while those that involve multi-particle excitations paint an interesting and complex picture of interplay between single-particle excitations, collective pairing, and deformation. This presents an interesting challenge for future theory.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2022
