Vibration-rotation spectra and molecular force field of methylene fluoride and methylene fluoride-d2

Infrared spectra of CH₂F₂ and CD₂F₂ have been measured under a medium resolution. The vibration-rotation bands of CD₂F₂ fundamentals have been analyzed and the assignment for the fundamentals of CD₂F₂ is given. In addition, a number of overtone and combination bands are observed for CH₂F₂, which helps to clarify the vibrational assignment for CH₂F₂. A normal coordinate treatment has been carried out: The force constants in a modified Urey-Bradley as well as the general valence force fields have been determined, the vibrational frequencies and the centrifugal distortion constants obtained from microwave spectroscopy being used. The force constants of the methylene fluoride molecule are discussed in connection with those of the related molecules. Special features of the CH₂F₂ and CD₂F₂ spectra are also described.