%AKim, K.%AAdhikari, G.%Ade Souza, E.%ACarlin, N.%AChoi, J.%AChoi, S.%ADjamal, M.%AEzeribe, A.%AFrança, L.%AHa, C.%AHahn, I.%AJeon, E.%AJo, J.%AKang, W.%AKauer, M.%AKim, H.%AKim, H.%AKim, S.%AKim, S.%AKim, W.%AKim, Y.%AKim, Y.%AKo, Y.%ALee, E.%ALee, H.%ALee, H.%ALee, H.%ALee, I.%ALee, J.%ALee, J.%ALee, M.%ALee, S.%ALee, S.%ALeonard, D.%AManzato, B.%AMaruyama, R.%ANeal, R.%AOlsen, S.%APark, B.%APark, H.%APark, H.%APark, K.%APitta, R.%APrihtiadi, H.%ARa, S.%ARott, C.%AShin, K.%AScarff, A.%ASpooner, N.%AThompson, W.%AYang, L.%AYu, G.%Anull%BJournal Name: The European Physical Journal C; Journal Volume: 81; Journal Issue: 8; Related Information: CHORUS Timestamp: 2023-01-07 11:31:59 %D2021%ISpringer Science + Business Media %JJournal Name: The European Physical Journal C; Journal Volume: 81; Journal Issue: 8; Related Information: CHORUS Timestamp: 2023-01-07 11:31:59 %K %MOSTI ID: 10306794 %PMedium: X %TIdentification of new isomers in $$^{228}$$Ac: impact on dark matter searches %XAbstract

We report the identification of metastable isomeric states of$$^{228}$$228Ac at 6.28 keV, 6.67 keV and 20.19 keV, with lifetimes of an order of 100 ns. These states are produced by the$$\beta $$β-decay of$$^{228}$$228Ra, a component of the$$^{232}$$232Th decay chain, with$$\beta $$βQ-values of 39.52 keV, 39.13 keV and 25.61 keV, respectively. Due to the low Q-value of$$^{228}$$228Ra as well as the relative abundance of$$^{232}$$232Th and their progeny in low background experiments, these observations potentially impact the low-energy background modeling of dark matter search experiments.

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