Millimeterwave Spectrum and Dipole Moment in the ν5, ν6, and ν9Excited States of Ketene: Comparison toab InitioResults for Ketene and Ketene-d2

Abstract

Rotational and centrifugal distortion constants as well as dipole moments in the three lowest-lying vibrational states of ketene, ν5, ν6, and ν9, have been determined from millimeterwave measurements in the range 40–165 GHz. The rotational constants, in theS-reduction, are (in MHz):A(51) = 311981,A(61) = 289864,A(91) = 228700,B(51) = 10291.373,B(61) = 10284.964,B= 10331.814,C(51) = 9940.304,C(61) = 9934.975,C(91) = 9935.051. Dipole moments are (in D): μgs= 1.42429, μ(51) = 1.37408, μ(61) = 1.40433, μ(91) = 1.42545. The present measurements and our previous data on ketene-d2[J. Dooseet al., Z. Naturforsch. A44,538 (1989)] have been compared to recentab initioresults [A. L. L. East,J. Chem. Phys.102,8506 (1995)]. The agreement between experimental and theoretical vibration–rotation interaction constants is generally good with some notable exceptions, especially for ketene-d2.