Abstract
The 9.2 keV nuclear transition in Th-227 was studied in the beta(-)-decay of Ac-227 by means of the internal conversion electron spectroscopy to clarify the spin-parity assignment of the ground state and the two lowest excited states of Th-227. The transition multipolarity was proved to be of mixed character M1+ E2 and the spectroscopic admixture parameter delta(2)(E2/M1) = 0.695 +/- 0.248(vertical bar delta(E2/M1)vertical bar = 0.834 +/- 0.149) was determined.
Nonzero value of delta(E2/M1) questioned the present theoretical interpretation of low-lying levels of Th-227. Calculations performed prefer the 1/2(+), 3/2(+), and 3/2(+) sequence instead of the adopted 1/2(+), 5/2(+) and 3/2(+) one for the 0.0, 9.2, and 24.3keV levels, respectively. (C) 2021 The Author(s).
Published by Elsevier B.V.