Early Universe

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Helonium Explained: The Real Story of HeH⁺ and the Universe’s First Chemistry

Introduction The name sounds like an element. It is not. HeH⁺ is the helium hydride ion, a positively charged molecular ion made from helium and hydrogen. Its systematic name is hydridohelium(1+). Scientists study it because early-Universe models place this ion near the very start of molecular chemistry. Its story spans a century. Laboratory evidence appeared in 1925. Astronomers found it…