Multidimensional nonlinear optical spectroscopies for chemical analysis

A central problem in analytical chemistry is the identification of components in complex mixtures and their relative concentrations. While many methods exist to accomplish this, no single methodology presently offers extremely high sensitivity, selectivity, and dynamic range. Recent advances in the generation of stable, tunable laser sources in the mid-infrared have allowed the development of optical analogues to 2-D NMR which probe the couplings between vibrational transitions. As in NMR, these couplings are indicative of the structure and composition of the samples under study. One of these novel 2-D optical methods, known as doubly vibrationally enhanced (DOVE) spectroscopy, shows great promise as a highly selective, sensitive method of probing vibration/vibration coupling, with time resolution on the order of picoseconds. In this work, a DOVE spectrometer has been designed, constructed, and implemented. DOVE spectroscopy has been quantitatively analysed and issues of spectral reproducibility have been addressed. The sensitivities of the method to the experimental parameters are explored, and the development of protocols to ensure reproducibility has allowed proof-of-principle experiments to be carried out on simple liquids. The method was carried forward to produce the first-ever DOVE spectra of the vibrations of solvated amino acids, providing evidence that the method is viable for fingerprinting and structure determination. The variation of 2-D spectra in the time domain is also explored, suggesting the possibility of the use of DOVE spectroscopy as a probe of molecular dynamics. Improvements to the methodology which will make DOVE spectroscopy comparable to existing analytical methods have been proposed.Imperial users onl