Perturbed energy eigenvalues of the Salpeter equation in the oscillator-representation method

On the basis of the oscillator-representation method, we obtain the energy eigenvalue formulae up to the second order in the perturbation Hamiltonian for the 1S-6S, 1P, 2P, 1D and 2D states of the heavy quarkonia. The applica tion of the formulae to the 1S-6S states in the linear confining potential suggests that we cannot neglect the effect of the relativistic kinetic term s on the energy eigenvalues in the excited states of the charmonia.