We have studied the characteristics of selective adsorption resonances (SAR) for helium scattering from the highly corrugated Xe/Ag(111) surface. A time-dependent quantum mechanical procedure developed previously for the study of resonances in gas-phase molecular collisions was employed. Converged resonance positions, lifetimes, partial widths, and resonance wave functions were obtained for states lying below 20 meV. The zero-order separable description of SAR was found to fail badly for the assignment of the states as well as for their energies and lifetimes, as expected. However, it was found that the separable model improves noticeably for SAR's with higher energy and for those states localized farther from the surface. More sophisticated separable models have been developed which can improve the agreement with exact results to some degree. The dynamical characteristics of SAR states are analyzed in detail and the role of symmetry is discussed. Energies and lifetimes along the bands of SAR were also generated.