This year, several isotopes were newly discovered or characterized - and, as expected, these are very short-lived atomic nuclei of interest for research.
In June 2026, a Japanese research group reported the first-ever use of a lead-208 primary beam to search for previously unknown nuclides at the RI Beam Factory (RIBF). The experiment aimed to extend the boundaries of the nuclide chart on both the proton-rich and neutron-rich sides for elements with atomic numbers above Z = 50. To achieve this, a 208Pb beam accelerated to 345 MeV per nucleon was directed at a beryllium target, producing the target nuclei via projectile fragmentation. The reaction products were subsequently separated and unambiguously identified on an event-by-event basis using the BigRIPS in-flight separator and a detector system capable of measuring time-of-flight, energy loss, and magnetic rigidity. During the experiment, 22 new isotopes were observed for the first time, thereby extending the known nuclide chart in both the proton-rich and neutron-rich directions: cerium-118, praseodymium-120, holmium-179, erbium-181, erbium-182, thulium-184, thulium-185, thulium-186, ytterbium-188, ytterbium-189, lutetium-191, hafnium-152, hafnium-153, hafnium-193, hafnium-194, tantalum-154, tantalum-195, tantalum-196, tungsten-198, tungsten-199, rhenium-200, and rhenium-201.
A report on the discovery of berkelium-235 and its alpha-decay product, americium-231, appeared in March 2026. The discovery was made by irradiating a gold-197 foil with a beam of argon-40 ions.
Also in March, a predominantly Japanese research group published the results of a search for previously unknown neutron-rich isotopes in the region above the doubly magic nuclide nickel-78. The experiment was conducted at the RI Beam Factory (RIBF) of the RIKEN Nishina Center. To produce the nuclei in question, a uranium-238 beam accelerated to 345 MeV per nucleon was directed at a 4 mm thick beryllium target, with the reaction products generated via in-flight fission of the uranium beam. The fragments were subsequently separated using the BigRIPS in-flight separator and unambiguously identified based on time-of-flight, magnetic rigidity, and energy loss. Eight neutron-rich isotopes were observed for the first time during this experiment; furthermore, the authors determined their production cross-sections: chromium-72, manganese-74, manganese-75, iron-77, cobalt-79, cobalt-80, copper-85, and gallium-90.
In February 2026, a Japanese research group published its findings regarding the discovery of 14 previously unknown proton-rich rare-earth isotopes. The experiment was conducted at the RI Beam Factory (RIBF), where a primary uranium-238 beam accelerated to 345 MeV per nucleon was directed at a 1 mm thick beryllium target. The newly produced fragments originated from projectile fragmentation and were unambiguously identified using the BigRIPS in-flight separator based on magnetic rigidity, time-of-flight, energy loss, and total kinetic energy. All 14 new isotopes were observed simultaneously during the same experiment; additionally, the authors determined their production cross-sections and compared them with theoretical predictions: Europium-132, Europium-133, Gadolinium-133, Gadolinium-134, Gadolinium-136, Terbium-136, Terbium-137, Terbium-138, Dysprosium-138, Holmium-143, Erbium-142, Thulium-144, Ytterbium-147, and Ytterbium-148.
In January 2026, seven new, extremely neutron-rich isotopes were identified at the RIKEN RI Beam Factory via in-flight projectile fragmentation of a 238U beam on a beryllium target. The discovery comprises the nuclides cesium-152, barium-155, lanthanum-158, cerium-159, cerium-160, gadolinium-173, and terbium-175, which were produced simultaneously and detected using the BigRIPS separator.
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The half-life values of the following isotopes or nuclides have recently been re-determined and published in the specialist literature (incomplete list; old value in square brackets):
The atomic weight of the element lead was previously given as 207.2 ± 0.1 u. Now the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW) recommends changing the standard atomic weight (i.e. relative atomic mass) to 207.2 ± 1,1 and the interval notation [206,14; 207.94]. The assignment of an interval for the new standard atomic weight of lead reflects the frequent occurrence of fluctuations in isotopic abundances in normal terrestrial Pb materials (source: IUPAC).
n-Hexane, Decamethyltetrasiloxane, Amphetamine, 3,4-Dihydroxyphenylacetaldehyde, 2-Phenylphenol, Diperoxochloric acid, 2,5-Cyclohexadiene-1-thione, 1,3-Dichloropropene
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