Al3+ · He: stability and spectroscopy

The complex between the trication, Al3+, and a helium atom is investigated using high-level ab initio calculations. In addition, the avoided crossing between the ground state Al3+ · He potential energy curve, and the lowest repulsive charge transfer state, Al2+⋯He+, is investigated using CASSCF + MRCI calculations: it is found that the avoided crossing is very sharp. Vibrational and rotational spectroscopic parameters are calculated. It is concluded that the Al3+ · He complex is kinetically stable and should be observable.