Ultra violet decomposition of surface adsorbed explosives investigated with infrared standoff spectroscopy

Abstract

Here we present a standoff spectroscopic technique where ultraviolet (UV) and infrared radiations are used in tandem to identify explosive residues on a surface 8 m away. Instead of analyzing byproducts, UV illumination induced changes in the adsorbates are investigated. The UV radiation is used to photodecompose the surface adsorbed explosive residues while the surface is probed with a tunable infrared quantum cascade laser. IR spectral changes generated after UV exposure are compared to the IR spectra before UV exposure to yield a signature similar to traditional transmittance plots for each explosive residue tested. Spectral variation the explosive compounds can be clearly identified with a surface concentration of 700 ng/cm2.

Keywords

Standoff
IR
UV
Explosive detection
Quantum cascade laser
Photodecomposition

Marissa E. Morales is a post-master researcher working in the Nanoscale Science and Devices Group at Oak Ridge National Laboratory. She obtained her Masters degree in Chemistry from the University of Puerto Rico Mayagüez Campus in 2008. Her main research interest is surface chemistry using spectroscopy and scanning probe microscopy as a characterization tool. Morales is currently working with identification of chemical residues on different surfaces using standoff and point spectroscopy.

Charles W. Van Neste is a research engineer at the Chemical and Materials Engineering department of the University of Alberta, Edmonton. He obtained his Ph.D. in Electrical Engineering from Tennessee Technological University in 2009. Dr. Van Neste was a post-doctoral fellow at the Oak Ridge National Laboratory prior to his present position at the University of Alberta. Dr. Van Neste's primary research involves the detection and identification of chemical residues using standoff and point sensing techniques. His areas of expertise include electronic instrumentation, wireless and pseudo wireless power transfer, and electric machine design.

Larry R. Senesac is a Staff Scientist at the Oak Ridge National Laboratory. He was a Research Assistant Professor at the University of Tennessee, Knoxville in the Department of Physics and Astronomy. He obtained his Ph.D. in Physics from the University of Tennessee, Knoxville in 1997. Dr. Senesac's research is currently focused on the detection and identification of chemical, biological, and explosive materials using micro-mechanical and nano-mechanical sensors as well as quantum cascade laser IR spectroscopy. His areas of expertise include: instrument design and electronics, infrared spectroscopy, and pattern recognition algorithms including artificial neural networks.

Satish M. Mahajan received his B.E. degree from the University of Poona in 1978. He obtained the M.S.E.E. degree from the state University of New York at Buffalo in 1983 and the Ph.D. degree from the University of South Carolina at Columbia in 1987. Since 1987 he has been on the faculty of the Electrical and Computer Engineering Department of Tennessee Technological University (TTU). Currently he is a Professor of the Electrical and Computer Engineering Department at TTU. His research interests are related to the physical phenomena of high-voltage and optoelectronic devices.

Thomas Thundat is a Canada Excellence Research Chair professor at the University of Alberta, Edmonton. He received his Ph.D. in physics from the State University of New York at Albany in 1987. Thundat is the author of over 280 publications in refereed journals, 45 book chapters, 33 patents and 7 pending patents, and over 130 invited talks. Dr. Thundat's research is currently focused on novel physical, chemical, and biological detection using micro and nano mechanical sensors.