Hypoflorous acid (HOF): A molecule with a rare (1,-2,-1) vibrational resonance and (8,3,2) polyad structure revealed by Padé-Hermite resummation of divergent Rayleigh-Schrödinger perturbation theory seriesстатья
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Дата последнего поиска статьи во внешних источниках: 4 июня 2021 г.
Аннотация:A quantitative study of the vibrational resonance phenomena of the HOF (hypoflorous acid) molecule for over 100 its lower vibrational energy levels was carried out using resummation techniques of the Rayleigh-Schrödinger perturbation theory (RSPT) divergent series. Anharmonic vibrational states of HOF were calculated by the matrix configuration interaction (VCI) method, the second-order Van Vleck operator perturbation theory (CVPT2), and the high-order RSPT series. CVPT2 predicts a weak Fermi resonance (0,1,–2) and a medium second-order resonance (1,–2,–1). Resummation of the high-order (λn, 0 ≤ n ≤ 203) divergent RSPT series, using multivalued quartic 40-th degree Padé-Hermite diagonal approximants up to terms O(λn+1) for a subset of low-lying states, restored their correct energies. Considering λ as a complex parameter, solution branch points were found as roots of discriminant polynomials. The coincidence of dominant branch points for pairs of states according to the Katz theorem and the condition |λ| = Re(λ)2 + Im(λ)2 ≤ 1, revealed resonance couplings. The block-diagonal polyad structure of studied states was reconstructed and the polyad quantum number P= (8,3,2) form determined as being good for all studied states, up to nearly 14,000 cm−1. Advantages of the developed technique for quantitative characterization of resonance and polyad phenomena are demonstrated.