On photochemical reactions of Am(5) in bicarbonate-carbonate solutions

The influence of UV radiation on Am(5) in solutions of sodium carbonate-bicarbonate with pH 9.00-11.40 has been studied by spectrophotometric method. At pH 9-10 a mixture of Am(4)+Am(6) is formed, but the degree of Am(5) transformation does not exceed 60-70%. The reaction order in terms of Am(5) is close to 1. Quantum yield of the reaction during photolysis by light with λ = 337 nm is estimated as 0.003. With increase in pH the reaction rate and degree of Am(5) transformation decrease. The reaction starts with absorption of UV light quantum by Am(5) carbonate complex. It is assumed that the reaction first stage is electron transfer either from water molecule to Am(5) in coordination sphere of excited carbonate complex of Am(5) or between two Am(5) ions in excimer, consisting of excited and non-excited carbonate complexes of Am(5). 10 refs., 2 figs