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| I-238 | |
|---|---|
| Name | I-238 |
| Mass number | 238 |
| Protons | 53 |
| Neutrons | 185 |
| Half life | ~? |
| Decay modes | beta decay, electron capture? |
| Natural abundance | trace |
I-238 is a theoretical or highly unstable isotope of iodine with mass number 238. It is discussed mainly in specialized nuclear physics, radiochemistry, and astrophysics literature alongside isotopes such as iodine-131, iodine-129, iodine-127, and isotopes of neighboring elements like tellurium-128, xenon-136, and antimony-125. Interest in this isotope arises in contexts that include nucleosynthesis pathways, nuclear reactors and particle accelerator experiments, and the study of heavy neutron-rich nuclides encountered in r-process scenarios such as the Kilonova associated with GW170817.
I-238 is categorized among neutron-rich halogen isotopes explored in experimental campaigns at facilities such as CERN, RIKEN, GSI Helmholtz Centre for Heavy Ion Research, Oak Ridge National Laboratory, and TRIUMF. Its existence is inferred from systematics of nuclide charts used by groups including the International Atomic Energy Agency, the National Nuclear Data Center, and collaborators in the ENSDF evaluations. Discussions of I-238 appear alongside isotopes produced in spallation experiments at sites like Los Alamos National Laboratory and in theoretical models developed by researchers at Lawrence Livermore National Laboratory and Argonne National Laboratory.
Predictions for I-238 use nuclear models such as the liquid drop model, shell model, and energy-density functional approaches practiced by researchers affiliated with Oak Ridge National Laboratory and Brookhaven National Laboratory. Expected properties include a high neutron-to-proton ratio compared with stable iodine isotopes like iodine-127, and implications for nuclear deformation considered by groups at University of York, University of Tokyo, and Stockholm University. Mass evaluations reference work from AME (Atomic Mass Evaluation) compilers and databases maintained by National Institute of Standards and Technology scientists. The nuclear spin and parity are uncertain but estimated from systematic trends studied by teams at CNRS, Max Planck Society, and University of Michigan.
Synthesis pathways proposed for I-238 include multi-nucleon transfer in heavy-ion collisions conducted at GSI Helmholtz Centre for Heavy Ion Research and GANIL, fragmentation of uranium or thorium beams at facilities such as RIKEN and CERN-ISOLDE, and neutron capture sequences in high-flux reactors run by Institut Laue-Langevin or Oak Ridge National Laboratory (HFIR). Accelerator-driven spallation at Los Alamos National Laboratory or isotope-separator online systems used by TRIUMF and ISOLDE could produce detectable quantities. Theoretical synthesis rates are computed within codes developed by researchers at European Organization for Nuclear Research collaborations and groups in Japan Atomic Energy Agency.
Predicted decay channels for I-238 draw on experimentally established patterns for heavy, neutron-rich iodine isotopes studied by collaborations at GSI, RIKEN, and CERN. Likely decay modes include beta-minus emission to isotopes of xenon and possible delayed neutron emission analogous to observations reported for isotopes investigated by NSCL at Michigan State University. Radiological characteristics such as beta spectra, half-life estimates, and associated gamma emissions are modeled by teams at Los Alamos National Laboratory and evaluated in the context of decay-data compilations by the IAEA and National Nuclear Data Center. Scenarios in which I-238 is produced exhibit short-lived activity relevant to experiments at Jefferson Lab and detectors used in astrophysical nucleosynthesis studies by groups at Princeton University and Caltech.
Direct practical applications for I-238 are limited by its extreme neutron richness and instability; however, it has relevance in fundamental research programs at GSI, RIKEN, TRIUMF, and CERN that investigate nuclear structure, shell evolution, and the limits of nuclear existence. Insights from I-238 studies inform models used by researchers at Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and Argonne National Laboratory in fields ranging from reactor physics to astrophysical r-process modeling pursued at institutions like University of Chicago and University of California, Berkeley. Data on isotopes in this mass region also support detector calibration work at Brookhaven National Laboratory and contribute to nuclear data libraries curated by IAEA and Nuclear Energy Agency scientists.
Handling of neutron-rich radioisotopes produced in accelerator or reactor environments follows protocols developed by International Atomic Energy Agency and national regulators such as the U.S. Nuclear Regulatory Commission and agencies in European Union member states. Laboratories such as Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, and Oak Ridge National Laboratory implement radiation protection measures, containment, and waste management procedures consistent with guidance from World Health Organization and International Commission on Radiological Protection. Transport and storage requirements adhere to standards promulgated by International Atomic Energy Agency and national transport authorities; access control and licensing practices are enforced by institutions like Department of Energy and equivalent regulatory bodies.
Research attention to extremely neutron-rich iodine isotopes intensified with experiments in the late 20th and early 21st centuries at facilities including GSI, RIKEN, TRIUMF, ISOLDE, and NSCL. Theoretical predictions emerged from collaborations at Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, Los Alamos National Laboratory, and university groups at University of Oslo and University of Copenhagen. Progress in radioactive ion-beam technology, supported by funding agencies such as the European Research Council, U.S. Department of Energy, and Japan Society for the Promotion of Science, enabled systematic exploration of the neutron drip line and informed models of r-process nucleosynthesis invoked in studies of events like GW170817 and supernovae investigated by teams at NASA and European Space Agency. Ongoing and future campaigns at next-generation facilities including FRIB and upgrades at RIKEN are expected to refine knowledge about isotopes in this region.
Category:Isotopes of iodine