Embedded chemicals detection using multiple frequencies excitation

In this paper, recent works of buried chemical detection system by stimulating and enhancing spectroscopic signatures with multi-frequency excitations are discussed. In this detection system, those multiple excitations, including DC electric field, microwave, CO₂ laser illumination and infrared radiation, are utilized and each of them plays a unique role. The Microwave could effectively increase the buried chemicals' evaporation rate from the source. The gradient DC electric field, generated by a Van De Graaff generator, not only serves as a vapor accelerator for efficiently expediting the transportation process of the vapor release from the buried chemicals, but also acts as a vapor concentrator for increasing the chemical concentrations in the detection area, which enables the trace level chemical detection. Similarly,CO₂ laser illumination, which behaves as another type vapor accelerator, could also help to release the vapors adsorbed on the soil surface to the air rapidly. Finally, the stimulated and enhanced vapors released into the air are detected by the infrared (IR) spectroscopic fingerprints. Our theoretical and experimental results demonstrate that more than 20-fold increase of detection signal can be achieved by using those proposed technology.