51³Ô¹Ï

Has Peter B. Baker not heard of alpha particles ("Compound the error", Letters, 26 January)? These are helium nuclei. Just add electrons. No need for chemistry, alchemy or nuclear fusion: radioactive fission can do the job. University College London's Ray Dolan presumably already knew this and thought it too obvious to mention.

Dave Kimber, St Neots, Cambridgeshire