The ν1 and v5 bands of D2CO and improved ground state constants

Abstract

The symmetric and antisymmetric C—D stretching vibrations of D2CO, the ν1 and ν5 fundamental bands, have been measured with high-resolution spectrometers. The region near the origin of the ν1 band, 2026–2087 cm−1, has been recorded by a tunable, diode laser spectrometer with Doppler-limited resolution and an accuracy of about 0.001 cm−1. The measurements were extended to the region between 2000 and 2300 cm−1 using a BOMEM Fourier transform spectrometer at the University of British Columbia. The limit of instrumental resolution was 0.004 cm−1.About 600 lines were assigned to the ν1 fundamental band and more than 1000 to the ν5 band. The band origins were found at ν1 = 2060.917 cm−1 and ν5 = 2162.922 cm−1. From the assigned transitions in the ν1 and ν5 bands, infrared combination differences for the ground state have been performed. By fitting the 1230 combination differences simultaneously with the published microwave data, we have achieved a complete set of very accurate molecular parameters for the ground vibrational state of D2CO.Both excited states ν1 = 1 and ν5 = 1 were found to be strongly perturbed by other states owing to Fermi and Coriolis interactions. Thus, only rough estimations for the rotational constants of these states can be given. Possible interactions will be discussed.