Diffuse reflectance pulse radiolysis of opaque samples

Abstract

Flash photolysis and pulse radiolysis techniques¹ have contributed substantially to our understanding of the harmful and beneficial effects of radiation. The development of extremely short pulsed excitation sources means that time resolution is no longer a serious limitation to the application of these methods^2,3. However, these methods have previously been restricted to transparent samples because changes in transmission of analysing light were measured following pulsed excitation. Recently^4–6, we have established that photochemical processes within opaque and highly scattering systems can be studied by observing changes in diffusely-reflected analysing light following laser excitation. Many of the most important radiation-induced processes involve non-transparent, heterogeneous systems, for example, most biological systems. We report here the first successful ‘diffuse-reflectance pulse radiolysis’ experiments in which we demonstrate that time-dependent absorption spectra of short-lived species can now be measured for opaque samples following pulse radiolysis.