We present a mathematically rigorous method for solving three-atomic b
ound state and scattering problems. The method is well suited for appl
ications in systems where the interatomic interaction is of a hard-cor
e nature. It has been employed to obtain the ground-and excited-state
energies for the helium trimer and to calculate the scattering phase s
hifts and wavefunctions for the He atom-se dimer at ultra-low energies
. (C) 1997 Published by Elsevier Science B.V.