INDIRECT 248 NM 20 NS PHOTOLYSIS OF ALIPHATIC AMINO-ACIDS IN AQUEOUS-SOLUTION

The photodecomposition of several aliphatic amino acids, glycine, vali ne (Val), leucine and methionine and a dipeptide (Val-Val), was studie d in neutral aqueous solution using 248 nm 20 ns laser pulses which ar e focused to the intensity of 4 x 10(12) W m(-2). Under these conditio ns water absorbs by a two-photon mechanism, yielding water radicals wh ich attack the solute molecules. A similarity of the action of water r adicals produced either by two-photon water photolysis or by gamma-rad iolysis was found in Ar- and N2O-saturated solution and under Ar in th e presence of tert-butanol (0.1 M). The efficiencies of photodecomposi tion (quantum yield and G value) were determined and compared with the G value of decomposition under gamma-radiolysis. With high-intensity 308 nm 20 ns laser pulses it was shown that the photodecomposition of leucine occurs via a two-photon absorption mechanism, but with signifi cantly smaller efficiency. (C) 1997 Elsevier Science S.A.