- First-ever measurement of the half-life for bound-state beta decay in 205Tl81+ ions.
- Solar neutrino capture cross-section for 205Tl calculated based on this measurement.
- New essential nuclear data for the LOREX geochemical solar neutrino experiment.
The Sun, the life-sustaining engine of Earth, generates energy through nuclear fusion while releasing a continuous stream of neutrinos—particles that serve as messengers of its internal dynamics. Although modern neutrino detectors unveil the Sun’s present behavior, significant questions linger about its stability over millions of years—a period that spans human evolution and significant climate changes. To address these uncertainties, the LORandite EXperiment (LOREX) stands as the final bastion of neutrino geochemical projects. This low-energy solar neutrino detector, with a record-low capture threshold of just 50.6 keV, aims to measure solar neutrino flux averaged over a remarkable 4 million years, corresponding to the geological age of the lorandite ore.
Neutrinos produced in our Sun interact with thallium atoms, present in the lorandite mineral (TlAsS2), and convert them into lead atoms. The lead isotope 205Pb is particularly interesting due to its long half-life time of 17 million years, making it essentially stable over the 4 million years timescale of the lorandite ore. As it is currently not feasible to directly measure the neutrino cross-section on 205Tl, researchers at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany, came up with a clever method to measure the relevant nuclear physics ingredients. For that they exploited the fact that fully ionized 205Tl81+ spontaneously decays by bound-state beta decay to 205Pb81+, delivering the information needed for the determination of the neutrino cross section.
The experimental measurement of the half-life of the bound-state beta decay of fully ionized 205Tl81+ ions was only possible thanks to the unique capabilities of the Experimental Storage Ring at GSI. As vapours of Tl are poisonous, 205Tl81+ ions were produced using nuclear reactions in the Fragment Separator. 205Tl81+ ions were then stored long enough for its decay to be observed and measured in the storage ring. “Decades of technological advancements were required to generate an intense and pure 205Tl81+ ion beam and measure its decay with high precision,” said Professor Yuri A. Litvinov, spokesperson for the experiment and principal investigator of the European Research Council Consolidator Grant ASTRUm.
“The team measured the half-life of 205Tl81+ beta decay as 291 (+33/-27) days, a key measurement which allows to determine the Solar neutrino capture cross-section”, explained Dr. Rui-Jiu Chen, a postdoctoral research associate involved in the project. Once the concentration of 205Pb atoms in the excavated lorandite minerals is determined by the LOREX project, we will be able to provide insights into the Sun’s evolutionary history and its connection to Earth’s climate over millennia. “This milestone experiment highlights the power of nuclear astrophysics in answering fundamental questions about the universe,” said Professor Gabriel Martínez-Pinedo and Dr. Thomas Neff, who led the theoretical work to translate the measurement to the required neutrino cross-section.
Dr. Ragandeep Singh Sidhu, the first author of the publication, emphasized its broader significance: “This experiment highlights how a single, albeit challenging, measurement can play a pivotal role in addressing significant scientific questions related to the evolution of our Sun.”
The GSI group led by Professor Yuri A. Litvinov, including Dr. Rui-Jiu Chen and Dr. Ragandeep Singh Sidhu, has maintained a longstanding collaboration with the division led by Professor Klaus Blaum at the Max Planck Institute for Nuclear Physics.
The publication is dedicated to the memory of late colleagues Fritz Bosch, Hans Geissel, Paul Kienle, and Fritz Nolden, whose contributions were integral to the success of this project.
Original publication:
Bound-state beta decay of 205Tl81+ ions and the LOREX project
R. S. Sidhu, G. Leckenby, R. J. Chen, R. Mancino, T. Neff, Yu. A. Litvinov, G. Martínez-Pinedo, G. Amthauer, M. Bai, K. Blaum, B. Boev, F. Bosch, C. Brandau, V. Cvetković, T. Dickel, I. Dillmann, D. Dmytriiev, T. Faestermann, O. Forstner, B. Franczak, H. Geissel, R. Gernhäuser, J. Glorius, C. J. Griffin, A. Gumberidze, E. Haettner, P.-M. Hillenbrand, P. Kienle, W. Korten, Ch. Kozhuharov, N. Kuzminchuk, K. Langanke, S. Litvinov, E. Menz, T. Morgenroth, C. Nociforo, F. Nolden, M. K. Pavićević, N. Petridis, U. Popp, S. Purushothaman, R. Reifarth, M. S. Sanjari, C. Scheidenberger, U. Spillmann, M. Steck, Th. Stöhlker, Y. K. Tanaka, M. Trassinelli, S. Trotsenko, L. Varga, M. Wang, H. Weick, P. J. Woods, T. Yamaguchi, Y. Zhang, J. Zhao and K. Zuber
Physical Review Letters 133, 232701. DOI: 10.1103/PhysRevLett.133.232701
Weblinks:
Group 'ASTRUm - Astrophysics with Stored Highy Charged Radionuclides' (GSI)
Theoretical Nuclear Astrophysics Group (GSI)
Division 'Stored and Cooled Ions' at MPIK