The available sets of crystal field parameters for erbium and thulium ethyl sulphates are used to calculate the Stark levels,g-values, Schottky specific heat, magnetic anisotropy, hyperfine interaction parameters and low temperature specific heat of these compounds. A comparison of these calculations with experimental data shows that one of these sets can be taken to be optimum within the accuracy of various measurements. These parameters along with the already optimised ones for other ethyl sulphates are discussed in the frameworks of electrostatic, angular overlap and superposition models for the crystalline fields. The antibonding energy parameter and ionicity are found to be different for light and heavy compounds and almost constant in either half of the series.

Energy eigenvalues and 〈x²〉_n for the oscillators having potential energyV(x)=(ω²x²/2)+λ<x^2r>x^2s have been determined for various values ofλ, r, s andn using renormalized hypervirial-Padé scheme. In general, the results show an improvement over the findings of earlier workers. Variation of the evaluated quantities and of the renormalization parameter withλ, r, s andn has been discussed. In addition, this potential has been employed as an illustrative example of the applicability of alternative formalism of perturbation theory developed by Kim and Sukhatme (J. Phys.A25 647 (1992)).