Pressure induces major changes in the nature of americium's 5f electrons

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