PNNL

Abstract

Infrared spectra of H2CO covering the 1.9 – 2.5 µm spectral domain have been recorded at very high resolution (0.005 cm-1) using Fourier transform spectroscopy. A thorough analysis of this spectral region has led to the observation and analysis of the v1+v6, v2+v4+v6, 2v3+ v6, v3+v5, v1+v2, v2+v5, 2v2+ v6 and 3v2 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 then possible to least-squares fit the observed energy levels to within a few thousandths of a wavenumber. The Obs. – Calc. 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.