Frequency and intensity analysis of the ν3, ν4, and ν6 bands of formaldehyde

Abstract

The infrared spectra of the ν3, ν4, and ν6 bands of formaldehyde in the region from 890 cm−1 to 1580 cm−1 have been obtained at high resolution using tunable diode laser (TDL) and Fourier transform-infrared (FT-IR) spectroscopy. The transition frequencies have been analyzed using a Hamiltonian including terms through sextic in centrifugal distortion and including five interstate vibration–rotation coupling terms. Excited state pure rotational transitions are also included in the data, and their frequencies are reproduced well. Individual measured line intensities are used to determine dipole derivatives and band strengths using the fully coupled, asymmetric top eigenvectors.

ExoMol line lists – VIII. A variationally computed line list for hot formaldehyde

“…Figure 5. Overview of our synthetic spectrum at T =296 K against HITRAN (Rothman et al 2013), Reuter et al (1989) and Zhao et al (2007). These are due to splitting caused by two transitions with the same quanta but with swapped Γ f and Γi giving the two lines very similar transition frequencies and absolute intensity which make them difficult to resolve experimentally.…”

“…High-resolution, room-temperature formaldehyde spectra have been well-studied in the laboratory (Johns & McKellar 1975;Brown et al 1979;Nakanaga et al 1982;Nadler et al 1987;Cline & Varghese 1988;Reuter et al 1989;Poulin et al 1996;Theulé et al 2003); the early work was reviewed by Clouthier & Ramsay (1983). Currently, the major source of publicly available spectroscopic data on H2CO is the HITRAN database (Rothman et al 2013) which has recently been updated to include long-wavelength data from the CDMS database (Müller et al 2005).…”

“…Residuals, in cm −1 , for line positions for the ν 3 , ν 4 and ν 6 bands. Observed data from Reuter et al (1989 …”

The Geometry and Force Field of Thioformaldehyde

“…Hence, these bands have the same symmetries on several occasions, albeit for different values of K a in some instances. Because of this, the specific "observed" rotational levels were extracted from the diagonalization of a 9 ‫ء‬ 9 matrix which was constructed by us from the recipe in (7). In particular, 4 and 6 have the same symmetries for both sets of K a ϭ Խ1Խ.…”

Evidence of Vibrational-Induced Rotational Axis Switching for HD12C16O: New High-Resolution Analysis of the ν5 and ν6 Bands and First Analysis of the ν4 Band (10-μm Region)

“…For this reason, the first three fundamental bands 4 (out-ofplane bending mode), 6 (CH 2 or CD 2 rock mode), and 3 (CH 2 or CD 2 bending mode) of the H 2 CO and D 2 CO isotopic species were investigated in detail by both infrared and microwave techniques ((6, 7) and references therein). The rotational energy levels belonging to the 4 1 , 6 1 , and 3 1 states are involved in a "triangle-type" interacting scheme of Coriolis interactions.…”