An approach for the description of vibrational excitations: Application to 11BF3

In this work an approach to describe vibrational excitations of molecules presenting a strong normal behavior in the framework of an algebraic representation in terms of local operators is presented. In our method the Hamiltonian is first written in terms of symmetry adapted coordinates and momenta. As usual the G matrix as well as the potential are expanded in terms of the symmetry adapted coordinates. The Hamiltonian obtained is recast in an algebraic representation through the introduction of the familiar symmetry adapted bosonic operators. An algebraic representation of the Hamiltonian in terms of local oscillators is obtained through a canonical transformation in terms of bosonic local operators. This realization is used to carry out an anharmonization procedure, where each bosonic operator is transformed into a new operator satisfying the su(2) algebra. This approach introduces new degrees of freedom that allows to improve the spectroscopic description, taking advantage of both the algebraic methods and the description in configuration space where the spectroscopic parameters are known in terms of the structure and force constants. In particular the vibrational description of the 11BF3 molecule is presented.