Energy levels and wave functions of weakly bound bosonic trimers using Pekeris coordinates and a symmetry-adapted Lanczos approach

An approach is presented for the accurate calculation of the energy levels of weakly bound bosonic rare gas trimers. A Pekeris coordinate system is used in order to avoid the interdependent range problem associated with internuclear distance coordinates. The present choice of coordinates also permits a straightforward treatment of boson symmetry and allows one to assess the importance of linear configurations through the calculation of one-body reduced distribution functions. The discrete variable representation is used and the eigenvalue problem is solved using a Lanczos recursion combined with projection operator techniques in order to extract totally symmetric states. Lennard-Jones systems corresponding to Argon and Neon are studied in order to assess the accuracy of the method by comparing them with those of recent benchmark calculations. The approach allows the accurate calculation of several bound states. Calculations are also performed for the case of a Morse interaction potential and the results are compared to those studies based on the commonly used internuclear distance coordinates. The present approach is found to be more accurate. (C) 2003 American Institute of Physics.