Broadband Rotational Spectroscopy for Molecular Structure and Dynamics Studies

Abstract

Abstract Recent technological advances enabled the development of a new broadband Fourier transform microwave spectrometer in 2006. Since then, more than 15 broadband spectrometers have become operational worldwide and have also been extended to the millimeter wave and the terahertz frequency range. In the experiment, the microwave frequency is linearly swept within a short chirp covering up to 12 GHz so far. This chirped pulse efficiently polarizes the molecular sample at all frequencies lying within this frequency range. Fourier transformation of the molecular response from the time domain to the frequency domain gives the broadband rotational spectrum. This new instrument removes one of the major disadvantages of cavity-based Fourier transform microwave spectroscopy, which has been its slowness. As a consequence, rotational spectroscopy is now concentrating on even larger and more complex molecules. Also double-resonance experiments are now facilitated. Furthermore, the broadband technique opens the door towards new directions of rotational spectroscopy, i.e., towards dynamics studies such as the investigation of isomerization reactions.