AbstractsChemistry

Chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is a powerful technique for molecular detection, identification and structural characterization for gas-phase molecules and molecular complexes. The broadband nature of the technique allows for simultaneous detection of all species populated in the pulsed jet sample with sufficient intensity. Recent developments of the CP-FTMW technique at low frequency, namely 2-18 GHz, have ushered in a new generation for microwave spectroscopy-enabled structure determination of molecules and molecular complexes, where systems with as many as 20 heavy atoms can be structurally characterized to better than 0.1 Å precision. A selection of studies illustrating the power of CP-FTMW spectroscopy in the 2-18 GHz region for structure determination are described. These studies include structural characterization of a molecule with high conformational flexibility as well as molecular clusters containing strong interplay between electrostatic and dispersive interactions, as well as weakly bound van der Waals binding characteristics. The sensitivity afforded by the CP-FTMW technique enables detection of isotopologues in natural abundance, which enables direct structure determination of a target molecular system by means of Kraitchman’s equations or least-squares structure fitting algorithms. Use of modern quantum chemistry techniques for analyzing intermolecular interactions, such as symmetry adapted perturbation theory (SAPT) and dispersion corrected DFT, is emphasized, as well as its use for accurate and efficient structure prediction in the context of automated broadband spectral assignment.