2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/153337We present a mathematically rigorous method for solving three-atomic bound state and scattering problems. The method is well suited for applications in systems where the inter-atomic interaction is of a hard-core nature. It has been employed to obtain the ground- and excited-state energies for the Helium trimer and to calculate, for the first time, the scattering phase shifts and wave-functions for the He atom-He dimer at ultra-low energies.9 pages, main file 21 kB, 1 eps and 4 ps figuresChemical PhysicsNuclear Theorytext