Rotational energies of plar symmetric-top molecules in high electric fields

Fast and accurate method for summation of divergent series

“…Such applications require sufficiently accurate energy levels in terms of the quantum numbers and molecular parameters. Because Rayleigh–Schrödinger perturbation theory yields suitable analytical expressions, there has been great interest in the calculation of perturbation corrections for both the weak‐field 31–38 and the strong‐field expansions 36–41.…”

Alternative treatment of rotational quantum systems

“…Perturbation theory is often used because it yields reasonably accurate analytical expressions [2,5,6]. To this end, the hypervirial perturbative method [6] is found to be most suitable. The main disadvantage of the perturbation calculation is that the convergence radius of the Rayleigh-Schr6dinger series is finite [7] although it seems to be large enough for most physical applications.…”