Research Interests Education
- B.S., 1995, Beloit College
- Ph.D., 2001, University of Pittsburgh
- Postdoctoral Researcher, 2001-2003, National Institute of Standards & Technology
- CHE 106 / 116: General Chemistry
- CHE 150: General Chemistry for Engineers
- CHE 356: Physical Chemistry II Lecture
- CHE 357: Physical Chemistry Laboratory
- CHE 546: Molecular Spectroscopy and Structure
- CHE 645: Quantum Mechanics in Chemistry
When considered in three dimensions, the potential energy surface governing the conformational flexibility of a molecule resembles a mountain range containing peaks, valleys, and passes. Knowledge of this landscape is critical for understanding molecular structure and dynamics. Terahertz (1 THz ≈ 33.33 cm-1 ≈ 300 µm) or far-infrared spectroscopy directly maps the routes that a molecule traverses in its journey from one valley to another by probing the large-amplitude, delocalized molecular motions that are responsible for structural change. Our research program addresses fundamental questions about molecular level processes using both frequency- and time-resolved THz spectroscopy in conjunction with high-level molecular modeling. The following is a description of several projects that exemplify the various capabilities of ultrafast THz spectroscopy.
surface for α-terthiophene.
One research project is the study of the torsional potential energy surfaces of flexible molecules, in particular, thiophene oligomers. These molecules serve as model systems for understanding the properties of conjugated polymers (polythiophene) used in molecular electronics. Due to extended conjugation, the electronic properties of these molecules are strongly correlated with their flexibility along the ring-ring torsional coordinates. Terahertz spectroscopy directly probes the torsional vibrations of these thiophene oligomers, thereby providing a direct map of the potential energy surface of the important ring-ring interactions.
A related research project is the study of light-induced structural changes in molecules and molecular clusters. The systems of interest range from thetrans→cis photoisomerization of azobenzene to excited-state double-proton transfer in the 7-azaindole dimer. We study these dynamics by initiating the event with a femtosecond pulse of UV light and then monitor changes in the low-frequency vibrations with a femtosecond THz probe pulse. These experiments offer exceptional insight into excited-state potential energy surfaces since they directly probe the vibrational motions along the actual coordinates of interest.
The Korter group is also investigating the use of THz radiation for the non-invasive and non-destructive detection and identification of concealed threats such as explosives, biological agents, and chemical agents. Terahertz radiation interacts strongly with high-dielectric substances such as water, but transmits with little attenuation through materials such as plastic, cloth, and paper. Consequently THz radiation, like X-ray radiation, can be used for non-invasive imaging. Unlike X-rays, it is low-energy and non-ionizing, which minimize deleterious health effects. Our research efforts range from developing new THz sources and sensors to improving our understanding of the chemical origins of THz spectra.
- Hakey, P. M.; Allis, D. G.; Ouellette, W.; Korter, T. M. Cryogenic Terahertz Spectrum of (+)-Methamphetamine Hydrochloride and Assignment Using Solid-State Density Functional Theory. J. Phys. Chem. A 2009, 113(17), 5119-5127.
- Fedor, A. M.; Allis, D. G.; Korter, T. M. The terahertz spectrum and quantum chemical assignment of 2,2'-bithiophene in cyclohexane. Vib. Spectrosc. 2009, 49(2), 124-132.
- Allis, D. G.; Hakey, P. M.; Korter, T. M. The solid-state terahertz spectrum of MDMA (Ecstasy) - A unique test for molecular modeling assignments. Chem. Phys. Lett. 2008, 463(4-6), 353-356.
- Allis, D. G.; Zeitler, J. Axel; Taday, P. F.; Korter, T. M. Theoretical analysis of the solid-state terahertz spectrum of the high explosive RDX. Chem. Phys. Lett. 2008, 463(1-3), 84-89.
- Allis, D. G.; Korter, T. M. Development of computational methodologies for the prediction and analysis of solid-state terahertz spectra. International Journal of High Speed Electronics and Systems 2007, 17(2),193-212.
- Brown, E. R.; Bjarnason, J. E.; Fedor, A. M.; Korter, T. M. On the strong and narrow absorption signature in lactose at 0.53 THz. Appl. Phys. Lett. 2007, 90(6), 061908/1-061908/3.