Matrix-isolation infrared study of acetaldehyde: Host-dependent vibrational features

Spectral features of CH3CHO in inert gas matrices (Ar, Kr and N2). [Display omitted] •A comparative study of CH3CHO vibrational spectra in different matrices (Ar, Kr and N2).•Peculiarity of the CO stretching band in Ar matrix.•A quantitative assessment of The Fermi-diad of the CO strecthing band by ONIOM calculations. The infrared spectra of acetaldehyde were measured in inert gas matrices (Ar, Kr, and N2). The vibrational features were dependent on the host atoms. In particular, in the CO stretching region, the fundamental band (ν4) is bifurcated for Ar, whereas it remains isolated for Kr and N2. The bifurcation could be interpreted as a Fermi-diad where host–guest interactions in the Ar matrix cause the accidental energy tuning of ν4 and 2ν9 levels, which is in contrast with the energy detuning observed for the formic acid dimers reported previously [J. Chem. Phys. 128 (2008) 114310.].