Author Institution: Department of Physics, The Pennsylvania State UniversityThe infrared emission spectra at 4.5 ΞΌm of 13C16O and 12C180ββ have been measured at high resolution. The v β v - 1 sequence from v = 1 to v = 11 in 13C16O was recorded (next to the 13CO2β emission) using a small amount (150 mg) of 90\%-enriched 13CO2β mined with He and N2β in a d.c.-discharge in a slow-flowing system. The 1-0, 2-1, and 3-2 bands of 12C18O were detected in natural abundance in a CO-He discharge thanks to the high working resolution (0.015 - 0.020cmβ1, of our new 4.5 to vacuum spectrometer with a 40 cm, 31.6 lines/mm grating. The data were combined with recent laser heterodyne measurements to calculate a set of Dunham coefficients for the two isotopic molecules