Anharmonic corrections for linear triatomic molecules subject to the Rennet-Teller effect

The effects of vibrational anharmonic terms and of the gK -correction on the energy levels of a triatomic molecule in a degenerate electronic state are considered. The electronic wavefunctions are described using the approach first suggested in the original paper of Renner. Formulae for the anharmonic corrections in a number of different situations are derived. For an electronic Π state the corrections are given in the form where i runs over the various contributions and x 1, x 2, … depend on the anharmonic force constants. The functions Fi can be determined numerically (see equations (4.3) and 4.7)). For the case without spin-orbit interaction the Fi s are given explicitly to first order in ∈ in table 1. Further-more, the same results apply for levels with |K|=v 2+1 even if the spinorbit interaction is not negligible. Explicit results for levels with |K|