Fig. 1: Schematic of the experiment.

a, Target and ion-source unit releasing Ac to form AcF_x molecules from injected CF₄. b, All species are ionized by accelerated electrons within the anode volume and extracted across a voltage difference (40 kV) to ground potential. c–f, The ion beam is then mass-separated (c), cooled and bunched (d) before neutralization via charge exchange with sodium vapour in the charge-exchange cell (CEC), and laser resonance ionization (e). f, The time-of-flight spectrum of the ion beam with mass-to-charge ratio A/q = 246 after 2,000 revolutions in a multi-reflection time-of-flight mass spectrometer^23,49. The expected times of flight for ²²⁷Ac¹⁹F⁺ (half-life t_1/2 = 21.8 yr) and ²²⁷Ra¹⁹F⁺ (t_1/2 = 42.5 min) are shown in red and blue lines, respectively. The x axis is offset by the expected time of flight for ²²⁷Ac¹⁹F⁺. No molecules other than ²²⁷Ac¹⁹F⁺ were identified in the beam.

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