Structure and dynamics in ionic liquids and concentrated salt solutions: an ultrafast spectroscopy study

A combination of spectroscopic methods and symmetry considerations were used throughout the presented studies to investigate the terahertz spectra showing liquid dynamics in varied systems. Optical Kerr effect spectroscopy revealed clusters of different sizes in aqueous sodium thiosulfate solutions with non-Newtonian behaviour. In conjunction with terahertz infrared spectroscopy, optical Kerr effect spectroscopy showed the charge-ordered nature of butylammonium ionic liquids, which manifested through phonon modes in the terahertz spectra. In eutectic lithium thiocyanate solutions, a combination of mid-infrared spectroscopy, optical Kerr effect spectroscopy and X-ray scattering showed a separation into nanoscale water-rich and salt-rich domains at low temperatures. In summary, the use of terahertz spectroscopy on selected model system provides information on the dynamics governing the behaviour of liquids and solutions