THERE'S PLENTY OF TIME AT THE BEGINNING: TIME-RESOLVED AND ULTRAFAST GEOCHEMISTRY

Conventional studies in mineralogy and geochemistry that investigate the rates of transformations or chemical reactions generally are limited to the millisecond range, and hence cannot address a wide range of processes involving nucleation, molecular relaxation, heat transfer, phase transitions, aggregation, and electron transfer reactions that occur at much shorter time intervals. However laser optical pump-probe techniques have enabled investigation of optical-induced processes into femtosecond regimes, and now special x-ray sources will be enabling analogous investigations into condensed matter processes not accessible with optical techniques. Early studies have enabled crystal structure analysis of compounds with short-lived excited molecular clusters, revealing how energy transfer is processed both electronically and structurally. These types of investigations will ultimately be important in unraveling how many enzymatic reactions progress. Some of the simplest processes in geochemistry are actually comprised of a series of extremely rapid steps, such that true molecular analysis of the pathways, transition states, and mitigating influences is not possible without appropriately fast timing experiments. In this presentation the general synchrotron-based techniques are described and several examples of processes that may be profitably examined are given including reductive dissolution and oxidation, phase transformations, and melting. The inherent complementarity with techniques that can sense and identify fast processes, but cannot isolate separate transformation states (e.g. classical NMR, ESR, IR methods) is discussed.