麻豆淫院

The origin of lithium (Li), the third element of the periodic table, has long been shrouded in mystery. This element, commonly found in cosmic rays as two stable isotopes, ⁶Li and ⁷Li, is crucial to understanding the origins of the universe and the evolution of its chemical elements.

In , an international team of researchers used the Alpha Magnetic Spectrometer (AMS-02) aboard the International Space Station to measure the cosmic-ray fluxes of ⁶Li and ⁷Li based on data accumulated from May 2011 to October 2023.

Based on information from over 2 million nuclei amassed across 12 years, the team formulated a hypothesis that strengthens the case for one possible origin of lithium while challenging another previously accepted explanation.

The findings are published in 麻豆淫院ical Review Letters.

Lithium has at least three possible sources of origin: formed via collisions of heavier cosmic-ray nuclei, created during the Big Bang, and produced from the decay of beryllium (⁷Be) in low-mass stars or novae.

Despite its multiple origins, Li nuclei are rare in our solar system but quite common in cosmic rays. Both isotopes can trace their birth to cosmic ray collisions, though some studies suggest that ⁷Li might also have a primordial origin from the Big Bang. However, the amount of ⁷Li predicted by Big Bang nucleosynthesis doesn't match what is observed in stars or inferred from cosmic-ray data.

Over the past 50 years, several experiments measured the ⁷Li/⁶Li ratio, but there was a mismatch between previous measurements of lithium flux and current cosmic-ray propagation models.

Furthermore, most lithium isotope flux calculations were conducted below ~1.9 GV rigidity鈥攁 measure of how strongly a particle resists being deflected by magnetic fields, defined as momentum per nuclear charge.

The researchers of this study believed that taking a closer look at these discrepancies across a broader rigidity range could help clarify the origin of the Li isotopes. To achieve this, they conducted measurements with unprecedented precision within the rigidity range of 1.9 to 25 GV, collecting data from 9.7 脳 10^{5 6}Li and 1.04 脳 10^{6 7}Li nuclei.

The data were accumulated over 12 years by AMS-02, a device consisting of a supercooled magnet that creates a uniform magnetic field for bending the paths of charged cosmic particles as they move through five different detectors.

The results indicated that both ⁶Li and ⁷Li exhibited almost the same time variations across the entire rigidity range. Above ~4 GV, the time variations matched those of other cosmic ray nuclei, helium, carbon, nitrogen, and oxygen.

The isotopes also showed the same rigidity dependence above ~7 GV, which strongly supports the hypothesis that both stable isotopes are produced from the collisions of heavier cosmic-ray nuclei with the interstellar medium and rules out the presence of a significant primary source of ⁷Li in the flux.

This study addresses the fundamental questions about the origin of elements and paves the way for getting better insights into the cosmic-ray environment, critical for advancing space exploration and astronaut safety.

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