Knowledge Bank

Two methods allowing to determine, in a more satisfying way than before, the whole set of vibrational and rotational constants for linear polyatomic molecules are proposed. One of these methods uses the diagonal form of the Hamiltonian and the other one uses the Van Vleck's perturbation theory which has been discussed in detail by Shaffer, Nielsen and $Thomas.1$ Staring from a set of parameters obtained in a previous $work2$ and by using the diagnonalization method we have computed the vibration energies, the B and D constants for more than two hundred levels of the $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C15O2$ molecule. This computation includes \emph{l} type doubling and three accidental resonances related to the following coupling off-diagonal elements: .