Fourier Transform Microwave Spectroscopy – An Improved Tool for Investigation of Rotational Spectra

Like in other fields of spectroscopy, the introduction of Fourier transform techniques promoted microwave and millimeter wave rotational spectroscopy of molecular species. As the time scale is shorter than in nuclear magnetic resonance, the development had to wait for sufficiently fast instrumental components for this time domain spectroscopy. By investigation of static molecular gases in waveguide sample cells and of molecular species in a pulsed supersonic beam, the Fourier transform technique has greatly enhanced the potential of rotational spectroscopy. The field is still open for further improvements. The basic theory and the present state of the experiments will be given and illustrated by examples of investigated species.