Molecular motions are governed by the laws of quantum mechanics; i.e. the allowed energies of molecular rotation and vibration are quantized. We use and develop modern high resolution spectroscopic techniques to probe these discrete states of molecules. Spectra recorded in the far-infrared region of the electromagnetic spectrum (using synchrotron light from the Canadian Light Source) provides information about the spacing between vibrational states of molecules (and the rotational levels within each state) while our custom-built FTMW and cp-FTMW spectrometers at the University of Manitoba provide a detailed look at rotational states of molecules. Finding rotational transitions would require incredible amounts of time were it not for in silico methods that provide accurate molecular structures. We first predict the geometry of our molecule of interest and use this information to simulate the rotational and/or vibrational spectrum. Once a sufficient number of transitions have been accurately measured, we can fit the values to obtain a variety of parameters, including rotational constants, distortion constants and various interaction parameters. We use these parameters to extract precise structural information, to better understand various internal motions (such as vibrations and tunnelling) and derive some electronic properties (dipole moments). This information is critical to theoretical chemists who seek to to improve and refine existing models of molecular structure and motions. Another interesting application of our research is that our recorded spectra serve as catalogs for identifying these species in astrophysical and atmospheric environments in order to better predict and model the chemistry in remote regions. Below are some of the recent projects to be tackled by the hard-working and enthusiastic people of our research group. At any time, we are studying multiple molecules using a variety of techniques and consistently publishing our findings in peer-reviewed journals. Potential students and Postdoctoral Fellows interested in our research should not hesitate to contact Dr. van Wijngaarden by e-mail at firstname.lastname@example.org. Silacyclobutane (SCB, c-SiC3H8)Silacyclobutane is a four-membered ring with potential for use as a precursor for silicon carbide film formation via chemical vapour deposition. Of particular interest to our group is the ring puckering mode, in which the puckered ring inverts to its mirror image through a planar intermediate. The potential energy curve characterizing this motion is that of a double well with a 440cm-1 barrier and the vibrational energy levels below this barrier are tunneling split. This gives rise to tunneling in the microwave spectrum that we have recorded using our FTMW instrument.We have also characterized the vibrational spectrum of the ring puckering vibration and other low frequency vibrational modes using synchrotron light at the Canadian Light Source. The assignments of these rich spectra are in progress.1,1,1-trifluoro-2-butanone (TFB)The pure rotational spectrum of TFB was studied using our cp-FTMW instrument. The spectrum is consistent with trans ground state conformation, and our precise geometry determination required observation of both the parent isoptoplogue and the 13C substitutions at each unique carbon atom. Further, we have been able to characterize the barrier to the internal rotation of the terminal methyl group.Far-IR ro-vibrational spectrum of azetidinePrincipal axis system of SCB. The c-axis comes out of the plane.ab initio potential energy curve between three stable TFB conformersAzetidine (c-C3H6NH) We have studied the three lowest frequency vibrational modes, which provided surprising results due to the presence of inversion about the amine center. Such low frequency modes are particularly difficult to model due to their anharmonicity, and hence spectra in this range are of increased interest to experimentalists and theoreticians alike. We intend to expand our analysis to include several higher energy vibrational modes in order to refine our characterization of azetidine and contribute to the fundamental understanding of azetidine’s large amplitude motions.