Fourth-Order Rotational Corrections to the Effective Dipole Moments of Nonrigid Asymmetric Rotors

Abstract An expression for the fourth-order rotational correction terms of the effective dipole moments of nonrigid asymmetric rotors has been derived using the method of contact transformation. The treatment takes into account the large-amplitude bending motion. The correction terms have been calculated for the different bending states of the H 2 O molecule. A poor convergence of the rotational series for this molecule has been obtained and some different nonpolynomial forms for these series, obtained by different summation methods, have been proposed and tested.