Enhanced stability, low electron affinity, and high ionization potential ar
e the hallmarks of a "magic" cluster. With an electron affinity of 0.28 eV,
ionization potential of 11.43 eV, and a large binding energy, AlH3 satisfi
es these criteria. However, unlike other magic clusters that interact only
weakly with each other, two AlH3 clusters bind to each other with an energy
of 1.54 eV. The resulting Al2H6, while also a magic cluster in its own lig
ht, possesses the most unusual property that the difference between its adi
abatic and vertical detachment energy is about 2 eV-the largest of any know
n cluster. These results, based on density functional theory, are verified
experimentally through photodetachment spectroscopy. DOI: 10.1103/PhvsRevLe
tt.86.692.