2 pages, 1 table, 1 figure.-- PACS nrs.: 21.10.Tg, 23.20.Lv, 27.90.+b.The low-energy structure of Ac-231 has been investigated by means of γ, conversion electrons, γ-γ and γ-e- spectroscopy following the β(-)-decay of Ra-231. Here, we report on the precise determination of the Ra-231 β-decay half-life.Peer reviewed