Laser photolysis study of the triplet states of fulvic acids in aqueous solutions

Abstract

The spectral and kinetic characteristics of short-lived intermediates formed during the photolysis of aqueous and alkaline (0.1 mol l⁻¹ NaOH) solutions of fulvic acids (FA) were studied by the nanosecond laser photolysis technique. Laser photolysis of FA at 337 nm leads to the formation of short-lived triplet states of FA (³FA) with a quantum yield of about 1% and different relatively long-lived intermediates (with decay rate constants in deoxygenated solutions of 1.8 × 10³–2.1 × 10⁵ and 80–160 s⁻¹, respectively), which are characterized by absorption spectra with maximums at λ ≤ 400 nm. ³FA are quenched by atmospheric oxygen with rate constants of 5.4 × 10⁸–1.1 × 10⁹ l mol⁻¹ s⁻¹. Introduction of phenols into the solutions at concentrations up to 0.1 mol l⁻¹ has no appreciable effect on the decay kinetics of the detected intermediate products of FA photolysis.