Determination of such molecule parameters as dipole moment and the inertia moments relative to principal axes by the microwave spectroscopy method is performed in most cases through analysis of electromagnetic radiation absorption spectra in the range of 10-40 GHz, where transitions of molecules from one rotational energy level to another occur, thus leading to band structure of the spectra.

The microwave spectroscopy method is very accurate for relatively simple molecules but as the molecular weight increases the method's accuracy begins to be affected by vibrational-rotational interaction. This method makes it possible to determine, with high accuracy, geometric parameters of many two-, three- and four-atom molecules, and to study such interesting effects as inversion. The method is poorly suitable for nonpolar molecules and is used to study matter only in the gas phase.