| Popis: |
Differential Excitation Spectroscopy (DES) is a new pump-probe detection technique (patent-pending) which characterizes molecules based on a multi-dimensional parameterization of the rovibrational excited state structure, pump and probe interrogation frequencies, as well as the lifetimes of the excited states. Under appropriate conditions, significant modulation of the ground state can result. DES results provide a unique, simple mechanism to probe various molecules. In addition, the DES multi-dimensional parameterization provides an identification signature that is highly unique and has demonstrated high levels of immunity from interferents, providing significant practical value for highspecificity material identification. Dimethyl methylphosphonate (DMMP) is used as a simulant for G series nerve agents and thiodiglycol as a simulant for sulfur mustard (HD). Ab initio calculations were performed on DMMP for various rovibrational states up to J’ ≤ 3 and validated experimentally, demonstrating good agreement between theory and experiment and the very specific responses generated. Thiodiglycol was investigated empirically. Optimal detection parameters were determined and mixtures of the two materials were used to demonstrate the immunity of the DES technique to interference from other materials, even those whose IR spectra show significant overlap. |
