The free radical anion CH₃CHCOO^- - derived during high energy irradiation from a-alanine by deamination has been investigated until now mainly by EPR, in irradiated single crystals, for basic research or in completely randomized polycrystalline material for g-dosimetric purposes. It has been found by spectrophotometry of irradiated single crystals that the free radical absorbs light at l_max = 350 nm e = 1100 M^-1 cm^-1. The same radical anion is observed by pulse radiolysis of alpha-chloropriopionic or propionic anion in aqueous solutions by Cl resp. a-H-abstraction. Basic and applied aspects of the identity of the radical anion obtained in different ways are discussed, as well as consequences for dosimetric techniques.