The ionization thresholds for the metastable Ca(4s4p P-3(0)). RG((II0-)-I-3,v'' = 0) states (RG = Ar, Kr, Xe) have been determined by two-color photoionization via several Ca(4s5s S-3(1)). RG((3) Sigma(+),v') intermediate resonance states. From other experimental measurements and ab initio calculations, D-0[Ca(4s4p P-3(0)). RG((II0-)-I-3)] = 60 +/- 50 cm(-1), 120 +/-60 cm(-1), and 300 +/- 80 cm(-1)' for RG = Ar, Kr, Xe, respectively, from which D-0(CaRG(+)) are calculated to be 775 +/- 50cm(-1), 1244 +/- 60 cm(-1), and 1811 +/- 80 cm(-1) for Ar, Kr, Xe, respectively. Bonding in the CaRG(+) ions is discussed and compared to the bonding in the analogous BeAr+, MgRG(+), and BaAr+ ions. (C) 1997 American Institute of Physics.