Description of vibrational excitations of the OCS molecule using a local algebraic approach

A study of vibrational excitations of the OCS molecule in the framework of a polyad conserving local algebraic model is presented. The description starts establishing the Hamiltonian in configuration space in terms of normal modes and later on translated into an algebraic representation by introducing the bosonic realization for harmonic oscillator. Then a canonical transformation to local operators is applied, which in turn are mapped to $SU\left(2\right)$ Morse like ladder operators to take into account anharmonicities from the outset. The obtained Hamiltonian is given in terms of local operators suitable to be applied to any molecular system, even to molecules with strong normal mode behavior. Our approach represents an advantage over methods based on configuration space at this level of approximation. This approach is applied to the principal isotopologue of OCS. The vibrational description was carried out including 86 experimental energies with $\mathrm{rm}s=0.36{\mathrm{cm}}^{\text{-1}}$, with a Hamiltonian involving 22 spectroscopic parameters plus three external parameters associated with the depth of the local potentials. A study of the isotopologues shows a correlation between a normal/local parameter recently introduced and their spectroscopic properties.