Date of Award
Campus Access Dissertation
Chemistry and Biochemistry
Mark A Berg
When applied to a variety of multidimensional spectroscopies, the characteristic duration, peak power, and bandwidth of 50 femtosecond pulses gives them capabilities to extract information unattainable with first order techniques. Despite the resolution difficulty due to the bandwidth, it is demonstrated both theoretically and experimentally on two contrasting spectral regions that fully resolved Raman spectra can be extracted with 50 femtosecond pulses by simultaneously detecting in the time and frequency domains. The best way to interpret the time-frequency (TF) plot is to Fourier transform it into a frequency-frequency (FF) plot, with the second frequency axis giving the frequency difference between two peaks. For the 1000-1400 cm-1 region of nitrobenzene which contains four peaks, the congested TF plot gives all 6 expected FF peaks. When the sparser 2200-3000 cm-1 spectral range of acetonitrile is excited and detected in the matter, the strengths and limitations regarding the resolution of fine ambiguities are revealed. Having established this capability, the set-up is then extended into the DOVE range, where two infrared pulses replace the two visible pulses in order to excite and probe a coherence between and fundamental and combination band. Here the details of the set-up are discussed in detail, including generation, phase matching control, and pulse characterization. The other method discussed here is a 2nd order transient grating spectroscopy called MUPPETS, a method which enables distinction between homogeneous and heterogeneous sources of nonexponential rates. The specifics of this set up will be detailed, as well as the results of a run performed on cadmium selenide quantum dots. After removing a fast biexciton effect that existed in the first 10 ps, the nonexponentiality of the nanoparticles was found to be heterogeneous in nature, which in the decay range we examined (2 ns) is resultant from the surface trap states having a uniform distribution of barrier heights.
Kern, S. J.(2011). Multidimensional Spectroscopy With Femtosecond Pulses. (Doctoral dissertation). Retrieved from http://scholarcommons.sc.edu/etd/696