Most natural processes that separate isotopes appear to be mass dependent, with magnitudes of isotope separation roughly proportional to differences in mass. Recent analytical studies have found an increasing number of instances where isotope fractionation is disproportionate in mass, including the nuclear field shift effect first proposed by Jacob Bigeleisen to explain anomalous uranium isotope signatures observed in chemical exchange experiments. This effect is not mass dependent, but is caused by differences in nuclear volume and shape � and their influence on electronic structure and stability. This talk will focus on the application of relativistic electronic structure theory to the calculation of nuclear volume effects in molecules, and possible methods for extending the calculations to condensed phases.

Estimating isotope fractionation driven by nuclear size

243rd National Meeting (2012)

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