Binding energies and geometry of the 24Mg-He2 and 40Ca-He2 triatomic systems

The energies and geometry of the ²⁴Mg-He₂ and ⁴⁰Ca-He₂ triatomic complexes are studied using the hyperspherical coupled-channel method. With pairwise He-X (where X denotes Mg or Ca) potentials, we find that the ²⁴Mg-⁴He₂ and ²⁴Mg-³He-⁴He systems possess two bound states and the ²⁴Mg-³He₂ system possesses one, while the ⁴⁰Ca-⁴He₂, ⁴⁰Ca-³He₂, and ⁴⁰Ca-³He-⁴He systems are found to support four, three, and three bound states, respectively. The different energies and geometric behaviors are reported when the He atom changes from ³He to ⁴He for the He-He-²⁴Mg (⁴⁰Ca) isotopic combinations. We also study structures of excited states and find that for some excited states, they are quite different from the ground states.