The potential energy curves and spectroscopic constants of the ground and excited states of the RbAr van der Waals system have been determined using a one-electron pseudopotential approach. This technique is used to replace the effect of the Rb+ core and the electron-Ar interactions by effective potentials. The core-core interaction for Rb+Ar was incorporated using the accurate CCSD(T) potential of Hickling et al. [Hickling, H. L.; Viehland, L. A.; Shepherd, D. T.; Soldan, P.; Lee, E. P. F.; Wright, T. G. Phys. Chem. Chem. Phys. 2004, 6, 4233-4239]. This model reduces the number of active electrons of the RbAr van der Waals systems to just the single valence electron, permitting the use of very large basis sets for the Rb and Ar atoms. Using this approach, the potential energy curves of the ground and excited states dissociating into Rb(5s, 5p, 4d, 6s, 6p, 6d, and 7s) + Ar are calculated at the SCF level. Spin-orbit interaction was also considered within a semiempirical scheme for the states dissociating into Rb(5p) and Rb(6p). Spectroscopic constants are derived and compared with the available theoretical and experimental data. Such comparisons for RbAr show very good agreement for the ground and the first excited states. Furthermore, we have predicted the B-2 Sigma(+)(1/2) <- X-2 Sigma(+), A(2)Pi(1/2) <- X-2 Sigma(+), A(2)Pi(3/2) <- X-2 Sigma(+), A(2)Pi(3/2) <- X-2 Sigma(+), 5(2)Sigma(+) <- X-2 Sigma(+), 3(2)Pi(1/2) <- X-2 Sigma(+), and 3(2)Pi(3/2) <- X-2 Sigma(+) absorption spectra.