Date of Degree
PhD (Doctor of Philosophy)
Christopher M. Cheatum
Two-Dimensional infrared (2D IR) spectroscopy measures correlations and couplings of vibrational transitions. All 2D IR spectrometers are home-built instruments that require extensive expertise to build and operate. Zanni and coworkers recently demonstrated that direct IR pulse shaping can simplify 2D IR data collection and analysis (S. H. Shim, R. Gupta, Y. L. Ling, D. B. Strasfeld, D. P. Raleigh and M. T. Zanni, Proc. Natl. Acad. Sci. U.S.A. 106 (16), 6614-6619 (2009)).
A pulse-shaping 2D IR spectrometer will produce less signal strength than a traditional four-wave mixing 2D IR spectrometer. Therefore, despite the advantages it offers, direct IR pulse shaping has not been widely adopted in the 2D IR community. This thesis outlines all the necessary steps to construct a pulse shaping 2D IR spectrometer. Then, it presents a novel detection scheme that utilizes a CMOS visible array. The CMOS array costs only 1500USD, while an MCT array, used in most 2D IR spectrometers, normally costs >50,000USD. After a thorough description of the apparatus, this thesis presents several 2D IR studies. The first study is a quantitative comparison of the signal strength of a pulse-shaping 2D IR spectrometer utilizing CMOS visible array detection to the signal strength of a traditional four-wave mixing 2D IR spectrometer. The second study measures 2D IR spectra of the azido stretch of 15N-labeled 3-azidopyridine. The final study measures the cyanate (OCN-) anion in several polar protic solvents.
The comparison shows that rapid averaging, made possible with direct IR pulse shaping, overcomes the loss of signal strength. It is also shown that upconversion and CMOS visible array detection does not cause a measurable loss in the signal to noise ratio (S/N). The study of 15N-labeled 3-azidopyridine shows that the azido stretch is an effective indirect probe of the protonation state of the pyridine ring. The study of OCN- reveals non-Gaussian spectral diffusion dynamics in methanol, presents a simple analysis of the non-Gaussian dynamics, and provides a physical justification of the observed dynamics.
Copyright 2012 William Thomas Rock
Rock, William Thomas. "2D IR done cheaper, easier, and faster: design and applications." dissertation, University of Iowa, 2012.