Detailed spectroscopy of Ca46 : A study of the β− decay of K

Abstract

We report on high-statistics data from the β − decay of the 46 K J π = 2 − ground state taken with the GRIFFIN spectrometer located at the TRIUMF-ISAC facility. In total, 199 γ rays and 42 excited states were placed in the level scheme, and from the observed β feeding and angular correlations of pairs of cascading γ rays, it was possible to assign spins and parities to excited states and determine mixing ratios for selected γ rays. The level structure of 46 Ca is compared to theoretical predictions from a microscopic valence-space Hamiltonian derived from two-(NN) and three-nucleon (3N) forces. These calculations are in reasonable agreement with the experimental data and indicate that the protons in this region are not as inert as would be expected for semi-magic nuclei.

Structure of $^{46,47}$Ca from the $β^-$ decay of $^{46,47}$K in the framework of nuclear shell model

“…Our shell-model results with SDPF-MU interaction reported in this paper for the level scheme of 46 Ca are better than previous studies [30,45]. MBPT gives ∼ 1 MeV energy difference between theory and experiment for 3/2 − 1 state in 47 Ca [45].…”

“…We have used the nuclear shell-model to determine the nuclear structure properties of 46,47 K and 46,47 Ca. It has been found that including cross-shell excitations in the valence space is necessary in order to correctly reproduce the energy spectra of 46,47 K and 46,47 Ca [30,45]. So, we have used a phenomenological SDPF-MU interaction [54] for sdpf -model space in the shell-model calculations with 16 O as an inert core.…”

“…Recently, an experiment has been carried out at TRI-UMF in which high-statistic data from β − decay of ground state (g.s.) J π = 2 − of 46 K into 46 Ca has been measured with GRIFFIN spectrometer [30], where, 42 excited states were populated and β feeding branching ratios into excited states of 46 Ca were also observed. From analysis of these data, it was possible to assign spin-parity of excited states.…”

“…In Ref. [30], authors have extended the work of Holt el. al wherein they have used non-standard valence space for 46 Ca in which protons occupy s 1/2 d 3/2 f 7/2 p 3/2 orbitals and neutrons occupy s 1/2 d 3/2 f 7/2 p 3/2 p 1/2 orbitals above a 28 Si core.…”

“…In the present work we have calculated the log f t values for allowed and forbidden β − decay of 46 K and 47 K corresponding to the available experimental data of TRI-UMF experiment [30,31], using the shell-model with sdpf -model space. For these calculations, we have also extracted the effective value of g A using chi-square fitting method.…”