Intellectual Merit: This project investigates the use of differential reflectometry (DR) for the detection of trace explosives on the surfaces of materials and people. Preliminary results show that explosive materials display distinguishable spectroscopic characteristics when compared with a number of substances that could be found in or on the luggage of a typical traveler. Since the wavelength range lies close to the visible, there is no significant signal loss for detecting target at standoff distances, which is a problem, for example, with terahertz (THz) detection. Using experiments, the research systematically investigates and characterizes the differential reflection spectra of a large number of explosives and safe chemicals. Of interest are reproducibility of the results, how the reflectograms of various explosives differ, the possible influence of taggants or impurities, the detection of liquid explosives, whether a given explosive on different substrates yields identical reflectograms, the sensitivity of the technique, how the surface structure influences results, and if exposure to sunlight changes the differential reflectograms of explosives. The research also seeks to understand the optical DR spectra by performing molecular model calculations. From the calculated molecular orbitals, possible electron transitions are extracted and displayed as ultra-violet absorption spectra. The results are compared with the data obtained by experimental differential reflectograms.
Broader Impact: The technical aspects of this research have the potential to significantly improve safety and security. In addition, the activities will educate graduate students in basic science and research methods. Also undergraduate students from engineering and students from the business and law schools will participate in a project on "Explosives Detection Devices" as a project in the Integrated Product and Process Design (IPPD) program at the University of Florida. The IPPD project is intended to teach students how to design products and processes in small multi-disciplinary teams under the guidance of faculty and industrial liaison engineers.