Open-Shell Quantum Dots And Atoms In Nano-Cavities

In an open-shell configuration giving rise to states with distinct multiplicities, Hund's first rule, stating that the higher multiplicity state is lower in energy, is rather universally obeyed. However, it has been noticed long ago that although the inter-electronic repulsion is the interaction that drives this energy splitting, its expectation value, along atomic isoelectronic sequences, is higher in the higher multiplicity state, at low nuclear charges. This is not the case in typical multi-electron quantum dots. The difference between these systems is explained and the transition fron atomic to quantum dot-like behaviour in confined open-shell atoms is examined. Finally, the multiplet structure is studied for atoms embedded in a Debye plasma.