Pressure Induces Major Changes in the Nature of Americium's5fElectrons

Abstract

Americium occupies a pivotal position in the actinide series with regard to the behavior of $5f$ electrons. High-pressure techniques together with synchrotron radiation have been used to determine the structural behavior up to 100 GPa. We have resolved earlier controversial findings regarding americium and find that our experimental results are in discord with recent theoretical predictions. We have two new findings: (1) that there exists a critical, new structural link between americium under pressure and its near neighbor, plutonium; and (2) that the $5f$ electron delocalization in americium occurs in two rather than one step.