Infrared Intensities and Bond Moments in CO12O18

By using isotopically enriched samples, the three fundamentals and one overtone of CO16O18 have been located in the gas phase. Positions disagree with predictions of a simplified theory by somewhat more than experimental error, especially for the Fermi-resonant pair ν1 and 2ν20. Intensities were also measured on the Fermi-resonant pair, and the bond moment derivative thus calculated, 5.79×10—10 esu, is in excellent agreement with that determined from the ν3 vibration of the normal isotopic molecule. This result lends support to the simple bond-moment hypothesis for stretching vibrations. Intensities were also measured on the solid phases of CO16O18 and of N2O; the results are in poor agreement with measurements on the gas phase, though the frequencies are only slightly shifted.