Quantal approach to study the structure of triatomic I 2 ⃛ X (X = He, Ne) VDW clusters

Energy levels of I 2 ⃛ X van der Waals ( VDW ) molecules, where X is a rare gas atom (X = He, Ne) are obtained in an approximate way by using cofocal elliptic coordinates and taking the I 2 internuclear axis as a quantization axis. This is the starting point to study vibrational predissociation ( VP ) of larger I 2 ⃛ X n ( n ⩾ 2) clusters, where a good energetic description may provide accurate initial conditions from which trajectory calculations can be carried out.