Molecular Magnetic Moments and Susceptibility in Formaldehyde

High-resolution microwave spectroscopy has been used to measure the molecular Zeeman effect in formaldehyde where both ΔM = 0 and ΔM = ±1 transitions were observed. The magnitudes and signs of the diagonal elements of the g tensor were determined. The results for OCH2 are | gbb—gcc | = 0.08±0.03, gaa = −2.935±0.03, gbb = −0.17±0.05, and gcc = −0.11±0.05. These results combined with the value of the bulk susceptibility yield the following value depending on the ground-state wavefunction for OCH2: 〈ψ0 | Σiri2 |ψ0〉 = 14.61×10−16 cm2, where the sum is over all electrons. The average value of the diamagnetic susceptibility in OCH2 is χd = −41.3×10−6. The average value of the paramagnetic susceptibility is χp = 40.8×10−6. The anisotropy in the paramagnetic susceptibility along the O–C bond is χ⊥p—χ∥p = 5.6×10−6 where χ⊥p is perpendicular to the CH2 plane.