First results from CLARION2-TRINITY: Coulomb Excitation of ⁴⁹Ti and Emerging Collectivity

The first results from CLARION2-TRINITY, a new charged-particle and HPGe array are presented: Coulomb excitation of ⁴⁹Ti. Ti-49 can be treated as a neutron hole plus semimagic ⁵⁰Ti core within the particle-core coupling scheme. Reduced electric quadrupole transition probabilities, or B(E2) strengths, for the 2⁺×f_7/2 multiplet members and 1p-2h 3/2^- cross-shell excitation were measured. The total electric quadrupole strength of ⁴⁹Ti is compared to the B(E2;0⁺→2⁺) of the ⁵⁰Ti core in search of enhanced quadrupole collectivity, similar to that recently observed in ¹²⁹Sb relative to a ¹²⁸Sn core [1]. Both cases are near double-magic nuclei and have small core B(E2) values. The results are compared to shell-model calculations with state-of-the-art nucleon-nucleon interactions. Ti-49 shows a quenching of the total quadrupole excitation strength when compared to ⁵⁰Ti, in disagreement with both particle-core coupling scheme, and empirical expectations. Reasons for this reduction in E2 strength will be discussed, including cross-shell excitations and large wavefunction fragmentation.

[1] T.J. Gray, et al., Phys. Rev. Lett. 124, 032502 (2020)