On the elimination of spurious modes in algebraic models of molecular vibrations

Spurious states arise naturally in the description of molecular vibrational excitations. In the harmonic approximation such states can be projected ou t from the physical space exactly. This is in general not the case when anh armonic interactions are considered. We show that within the framework of t he symmetry, adapted vibron models which include anharmonicities from the o utset, these states can be removed in an exact fashion, (C) 1999 Academic P ress.