The high-resolution infrared spectrum of Kr-(CO2)-C-12-O-18 has been observed in the nu(3) band (2314 cm(-1)) region of (CO2)-C-12-O-18 with diode laser absorption spectroscopy of pulsed molecular beam. The vibrational band origin of Kr-(CO2)-C-12-O-18 corresponding to the nu(3) mode of (CO2)-C-12-O-18 shows a shift of Delta nu(0) = -0.86510(30) cm(-1) with respect to that of (CO2)-C-12-O-18. The geometrical parameters of the T-shaped ground-state average structure are determined to be R-KrC = 3.6204(11) angstrom and Theta(KrCO) = 83.51(10)degrees. The change in the CO2 intramolecular potential upon complex formation is derived from the observed red shift Delta nu o(0), and the isotope effects on R-KrC and Theta(KrCO) are reproduced by ab initio calculation. (c) 2005 Elsevier B.V. All rights reserved.