New Accurate Fit of an Extended Set of Saturation Data for the nu(3) Band of SF(6): Comparison of Hamiltonians in the Spherical and Cubic Tensor Formalisms.

An extended set of 321 frequencies of vibration-rotation lines of the nu(3) band of SF(6) has been measured by saturation spectroscopy using various isotopic species of CO(2). A least-squares fit of these data has been performed using an effective Hamiltonian written either with a spherical tensor or with a cubic tensor formalism. We have derived correspondence formulas between the parameters in the two approaches and checked that both formalisms give the same results up to the seventh order. Corrected parameters are given for the fit with a fifth-order Hamiltonian. An accurate representation of the band is obtained at the tenth order (standard deviation approximately 12 kHz) with a remarkable predictive power (better than 40 kHz) for J values </= 100. The convergence properties of the Hamiltonian power expansion are discussed. Copyright 2000 Academic Press.