The weakly bound Ca(4s4dσ 3D3)⋅Ar[3Σ+] state has been characterized by means of R2PI (Resonant Two-Photon Ionization) spectroscopy, using transitions from the Ca(4s4pπ 3P0)⋅Ar[3Π0⎯] metastable state prepared in a laser-vaporization/supersonic jet source. Because several of the vibrational levels are above the dissociation limit [to Ca(4s4d 3D3)+Ar(1S0)], it is concluded that there must be a substantial maximum in the Ca(4s4dσ 3D3)⋅Ar[3Σ+] potential curve (>200 cm−1) at large R (>4.0 Å). This is discussed, and shown to be consistent with our earlier ideas of “penetration” of outerlobes of electron density of metal atom excited states by RG (rare-gas) atoms. Perturbations observed, due to possible potential curve crossings with states of different electronic symmetry, are also discussed.