High resolution spectroscopy of H2 12C16O in the 1.9 to 2.56 µm spectral range

Abstract

Infrared spectra of H2CO covering the 1.9 µm–2.5 µm spectral domain have been recorded at high resolution (0.005 cm−1) using Fourier transform spectroscopy leading to the observation and analysis of the ν1 + ν6, ν2 + ν4 + ν6, 2ν3 + ν6, ν3 + ν5, ν1 + ν2, ν2 + ν5, 2ν2 + ν6 and 3ν2 bands. The line frequencies were calculated using effective (empirical) Hamiltonian models, which account for the main Coriolis and vibrational interactions. Using an interactive scheme it was possible to least-squares fit the observed energy levels to within a few thousandths of a cm−1. The observed–calculated differences do not match the spectral precision (∼0.0008 cm−1), but, given the congestion in the spectrum resulting from the density of the vibrational states as well as the large centrifugal distortion and Coriolis and anharmonic coupling effects, we believe that a reasonable agreement was obtained. From the fittings the following band centers were derived where the expanded uncertainties are one standard deviation (i.e. k = 1). Finally a number of line intensities were measured having uncertainties of about 25%, which permits the determination of the main terms appearing in the expansion of the transition moments. A comprehensive list of line frequencies and intensities has been generated.