A test of the concept of ‘charge localisation’ in methionine

A previous re-investigation of methionine has shown that the C₂H₅S]⁺ ion is generated via rather complicated routes from the molecular ion. This has been interpreted as evidence against charge localisation in the fragmentation of the title compound. Deuterium labelling, high resolution mass measurements and metastable transitions have revealed, however, that the formation of the C₂H₅S]⁺ ion is not in contradiction with the predicting capabilities of the concept of charge localisation.