DEGENERATE AND STRONGLY INTERACTING VIBRATIONAL STATES OF POLYATOMIC MOLECULES: THE PROBLEMS IN ROTATIONAL ANALYSIS AND DETERMINATION OF SPECTROSCOPIC CONSTANTS

$^{1}$ Vl.G. Tyuterev, V.I. Starikov, V.I. Tolmachev, Dokl. Akad. Nauk, v.297,No.2, p.345, 1987. $^{2}$ Vl.G.Tyuterev, J.P.Champion, G.Pierre, V.I.Perevalov, J.M.S., 120, 49 (1986).Author Institution: Institute of Atmospheric Optics, SB USSK Acad. Sci.The problem of processing of experimental vibration-rotation spectra in the case of strongly interacting vibrational states are discussed. Among them two aspects of convergence problems are considered in more details: a) convergence properties of expansions of effective Hamiltonians; b) convergence properties of least square fits. In order to improve convergence properties of a Hamiltonian more flexible developments may be applied. Nonpolynomial hamiltonian /1/ and interacting-state models are discussed in this context. A quality of a fit and extrapolation properties are improved, however, in many cases correlations between parameters and their ambiguities become more pronounced /2/ if interacting bands are treated together. The subject is to study the following question. How to obtain simultaneously good fit of experimental data and unambiguous physically meaningful values of spectroscopic parameters