The situation is modeled, in which two electronic states of a diatomic molecule are nonadiabatically coupled to each other as well as to other states, so that levels of the former two states can be registered, while the latter (perturbing) states are unobserved in an experiment. An example being explored is the model of the states 2³_g 4^1þ_g of Rb₂; the computation is done with the multichannel (3-channel, where the third channel represents an effective unobserved perturber) split operator method. Besides the typical resonance-like shifts of a part of the levels, the cases are observed, which cannot be explained within the approximation of a pair–wise resonant interaction. We tested a capability to analyze the synthetic data via an estimate of the interaction matrix element from the magnitudes of the resonance-like shifts combined with an iterative correction of the potential functions, as well as via the two-channel close-coupling calculation.