2018/04/01 by P. V. Borisyuk, Borisyuk, P. V., E. V. Chubunova +9
Physics and Astronomy · #Atomic and Subatomic Physics Research #FOS: Physical sciences #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th) #Optics (physics.optics) #Plasma Physics (physics.plasm-ph) #Quantum, superfluid, helium dynamics #Radioactive Decay and Measurement Techniques
paper · pdf · doi:10.48550/arxiv.1804.00299
openalex publication_date 2018/04/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The results of experimental studies of the low-energy isomeric state in the 229Th nucleus are presented. The work is consisted of several stages. During the first stage 229Th nuclei were excited with the inverse internal conversion to the low-lying isomeric level in plasma that was formed by laser pulse at the 229Th-containing target surface. Then thorium ions having excited nuclei were extracted from the plasma by an external electrical field and implanted into thin SiO2 film grown on a silicon substrate (that is a dielectric material with about 9 eV band-gap). Gamma decay of isomeric nuclei was registered during the second stage by the general methods of the electron spectroscopy after the photon-electron emission from the silicon substrate. Substitution of the photon registration with the electron one allowed us to increase the desired signal by several orders of magnitude and detect the 229Th nuclei decay. During the third stage the electron spectra from standard Xe VUV source was obtained that allowed determining the energy of photons. In order to prove that the detected signal is caused by isomeric 229Th nuclei decay a series of experiments was carried. The analysis of electron spectra gives the following results: the energy of the nuclear transition is Eis=7.1(+0.1-0.2)~eV, the half-life of the isomeric level in bare nucleus in vacuum is T1/2=1880±170~s, the reduced probability of the isomeric nuclear transition is BW.u.(M1;3/2+→ 5/2+)=(3.3±0.3)×10-2.