Microwave Zeeman Effect of Formaldehyde

Zeeman effects in the absorption spectra of formaldehyde H 2 CO, HDCO, and D 2 CO were studied in microwave region with magnetic field of 1500∼300 oersteds. The effective g -values in several rotational states and the elements of g -tensor g a a , g b b , and g c c of these molecules were determined. Dependences of the effective g -values on the rotational quantum numbers J , τ were consistent among these isotopically substituted molecules. The components of the g -tensors of these molecules have been found to be g a a =2.86±0.04 for H 2 CO, 2.00±0.05 for HDCO, and 1.46±0.05 for D 2 CO. They are extraordinarily large compared to those of other molecules already known. A brief qualitative interpretation is given.