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Abstract Radioactive nuclei with lifetimes on the order of millions of years can reveal the formation history of the Sun and active nucleosynthesis occurring at the time and place of its birth^1,2. Among such nuclei whose decay signatures are found in the oldest meteorites,²⁰⁵Pb is a powerful example, as it is produced exclusively by slow neutron captures (thesprocess), with most being synthesized in asymptotic giant branch (AGB) stars^3–5. However, making accurate abundance predictions for²⁰⁵Pb has so far been impossible because the weak decay rates of²⁰⁵Pb and²⁰⁵Tl are very uncertain at stellar temperatures^6,7. To constrain these decay rates, we measured for the first time the bound-state β⁻decay of fully ionized²⁰⁵Tl⁸¹⁺, an exotic decay mode that only occurs in highly charged ions. The measured half-life is 4.7 times longer than the previous theoretical estimate⁸and our 10% experimental uncertainty has eliminated the main nuclear-physics limitation. With new, experimentally backed decay rates, we used AGB stellar models to calculate²⁰⁵Pb yields. Propagating those yields with basic galactic chemical evolution (GCE) and comparing with the²⁰⁵Pb/²⁰⁴Pb ratio from meteorites^9–11, we determined the isolation time of solar material inside its parent molecular cloud. We find positive isolation times that are consistent with the others-process short-lived radioactive nuclei found in the early Solar System. Our results reaffirm the site of the Sun’s birth as a long-lived, giant molecular cloud and support the use of the²⁰⁵Pb–²⁰⁵Tl decay system as a chronometer in the early Solar System. 

Penning-trap mass spectrometry in atomic and nuclear physics has become a well-established and reliable tool for the determination of atomic masses. In combination with short-lived radioactive nuclides it was first introduced at ISOLTRAP at the Isotope Mass Separator On-Line facility (ISOLDE) at CERN. Penning traps have found new applications in coupling to other production mechanisms, such as in-flight production and separation systems. The applications in atomic and nuclear physics range from nuclear structure studies and related precision tests of theoretical approaches to description of the strong interaction to tests of the electroweak Standard Model, quantum electrodynamics and neutrino physics, and applications in nuclear astrophysics. The success of Penning-trap mass spectrometry is due to its precision and accuracy, even for low ion intensities (i.e., low production yields), as well as its very fast measurement cycle, enabling access to short-lived isotopes. The current reach in relative mass precision goes beyond δ m/ m=10 −8 , the half-life limit is as low as a few milliseconds, and the sensitivity is on the order of one ion per minute in the trap. We provide a comprehensive overview of the techniques and applications of Penning-trap mass spectrometry in nuclear and atomic physics.