Infrared Absorption of Formaldehyde at Low Temperatures: Evidence for Multiple Trapping Sites in an Argon Matrix

The infrared absorption of formaldehyde in both the polycrystalline and the monomeric form has been measured at 4 °K. In the latter case the molecules were suspended in an inert matrix of Ar or N 2 . The fine structure of the matrix spectra is discussed from the point of view of rotation of the monomers but this interpretation is ruled out in favor of one based on multiple trapping sites in the matrix.