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"The article refers to elements with atomic weights higher than 260, which would mean elements like lawrencium and rutherfordium; they all have half lives of le

"The article refers to elements with atomic weights higher than 260, which would mean elements like lawrencium and rutherfordium; they all have half lives of less than a day." Does the article really mean that? " r-process can produce atoms with an atomic mass of at LEAST 260 before they fission." https://en.wikipedia.org/wiki/Island_of_stability https://en.wikipedia.org/wiki/Island_of_stability and https://www.researchgate.net/publication/279166139_Charge_spectrum_of_superheavy_nuclei_of_galactic_cosmic_rays_obtained_in_the_OLIMPIA_experiment https://www.researchgate.net/publication/279166139_Charge_sp...

adrian_b 3y ago
According to current knowledge, the r-process can produce atoms with an atomic mass of at MOST 260, i.e. mainly up to fermium 257. Moreover, the nuclides with atomic mass close to 260, i.e. isotopes of einsteinium and fermium, would be produced in relatively small quantities in comparison with lighter elements. Exceeding 260 is highly improbable because such nuclei fission spontaneously extremely quickly, in milliseconds or microseconds, so the neutron flux would need to be much more intense than in nuclear explosions in order to produce a non-negligible equilibrium concentration. Most elements that are heavier than plutonium would decay before the materials containing them could aggregate into a planet (which may take at least a few million years). When the planets of the Solar System have formed, they probably still contained significant quantities of plutonium and neptunium, but then they have decayed quickly, leaving uranium as the heaviest surviving primordial element. While there might exist an island of stability for super-heavy nuclei of elements beyond any of those that have been synthesized artificially by ion collisions, for now there is no known natural process that could produce them in measurable quantities. By "stability" it is meant that the super-heavy elements might have lifetimes measured in years instead of milliseconds, not that they could be as stable as the already not very stable uranium or plutonium.

adrian_b 3y ago

According to current knowledge, the r-process can produce atoms with an atomic mass of at MOST 260, i.e. mainly up to fermium 257. Moreover, the nuclides with atomic mass close to 260, i.e. isotopes of einsteinium and fermium, would be produced in relatively small quantities in comparison with lighter elements. Exceeding 260 is highly improbable because such nuclei fission spontaneously extremely quickly, in milliseconds or microseconds, so the neutron flux would need to be much more intense than in nuclear explosions in order to produce a non-negligible equilibrium concentration. Most elements that are heavier than plutonium would decay before the materials containing them could aggregate into a planet (which may take at least a few million years). When the planets of the Solar System have formed, they probably still contained significant quantities of plutonium and neptunium, but then they have decayed quickly, leaving uranium as the heaviest surviving primordial element. While there might exist an island of stability for super-heavy nuclei of elements beyond any of those that have been synthesized artificially by ion collisions, for now there is no known natural process that could produce them in measurable quantities. By "stability" it is meant that the super-heavy elements might have lifetimes measured in years instead of milliseconds, not that they could be as stable as the already not very stable uranium or plutonium.