La radiolyse de l'eau et des solutions aqueuses : historique et actualité

Experiments showing that water is decomposed by the action of high-energy radiations date back to the first days of the discovery of radioactivity, a century ago. On the occasion of this anniversary, we have attempted to give a comprehensive account of the radiation chemistry of water and its solutions since its origin, with special emphasis on the various physical and chemical stages that led to the present state of this science. To this aim, we describe the effect of different intervening factors on the molecular and radical yields, including dissolved solute concentration, pH, radiation intensity (or dose rate), type and energy of the radiation, presence of oxygen, temperature, phase, and pressure. We also discuss briefly the chemical behavior of the free radicals produced in radiolyzed aqueous solutions. A good, albeit incomplete, description of the phenomena is obtained that leads to various perspectives concerning, on the one hand, the development of this science and, on the other hand, its potential for applications.Key words : radical chemistry, dilution curve, water, hydrated electron, hydroxyl and superoxide radicals, free radicals, radiolysis, chain reactions, molecular and radical yields, cell survival, linear energy transfer.

The radiation chemistry of aqueous solutions - I. The effect of changing linear energy transfer along a polonium α -particle track

Absolute G values for chemical change when various aqueous solutions are irradiated with α -particles from an external polonium source have been determined for different fractions ( x ) of the α -particle track spent within the solution. G(Fe 3+ ) for an aerated solution containing 1 mM ferrous ions and 0.1N sulphuric acid decreases from 5.0 at x =0.02 through a minimum value 3.65 at 0.11 x 0.01 and then increases to 5.94 at x = 0.525. The local value G(Fe 3+ ), defined as G(Fe 3+ ) for an element of track length a distance x R from the end of the track, where R is the range of the whole track in water, shows a similar but more pronounced dependence on x which is strongly reminiscent of the inverted Bragg curve for l. e. t. plotted against x in this medium, having a minimum of 3.2 5 ± 0.1 5 at x= 0.085±0.015. As x is increased G(Ce 3+ ) for an aerated 200 μM solution of ceric sulphate in 0.1 N sulphuric acid shows no minimum but increases from 1.0 at x =0.04 to 3.0 at x=0.25 and 4. 05 at x = 0.525. Thallous ions have no effect on G(Ce 3+ ) for x ≤ 0.45. G(H 2 O 2 ) for aerated water was found to be 1.22 ±0.06. It is concluded that very few hydroxyl radicals are available and that the intra-track reactions between H 2 O 2 and H as well as OH are very important and vary in extent as x is varied.