The Mg(3s3d sigma(3)D(J)). Xe((3) Sigma(+)), Mg(3s3d pi(3)D(J)). Xe((3) Pi(0+,0-)), and Mg(3s3d delta(3)D(J)). Xe((3) Delta(1)) excited states have been characterized via resonance enhanced two-photon ionization (R2PI) spectroscopy of transitions from the long-lived Mg(3s3p pi(3)P(J)). Xe((3) Pi(0+,0-)), metastable states of the MgXe van der Waals molecule. Because the excited Mg(3d) orbital is quite diffuse and the Xe atom can approach along the nodal axis of the aligned 3d orbital, minimizing repulsion, the MgXe(3s3d delta(3) Delta(1)) state (D-0= 3160 +/- 150 cm(-1)) is even more strongly bound than the MgXe+ core ion (for which D-0 = 2848 +/- 150 cm(-1)). The MgXe(3d sigma(3) Sigma(+)) state (D-0 = 1262 +/- 150 cm(-1)) and the MgXe(3d pi(3) Pi(0-)) state (D-0 = 1229 +/- 150 cm(-1)) are much less bound. However, the potential curves of these two states are quite different, and it is suggested that the MgXe(''3d sigma''(3) Sigma(+)) State is bound only because of substantial mixing of Mg(4p sigma) Rydberg character into the wave function. Interesting spin-orbit and spin-spin effects, detected and analyzed from the rotational structure of the vibrational bands, are attributed to mixing of some Xe character into molecular orbitals nominally of Mg* excited state character. (C) 1997 American Institute of Physics.