Vibrational overtone stretching transitions in trimethyl phosophate and triethyl phosophate - art. no. 65540D

The CH stretching overtone transitions of chemical warfare agents are of interest in the area of threat detection, including standoff threat detection, as many of these transitions occur near regions where small, efficient diode lasers operate. Further, detectors which operate in the regions where CH overtone transitions occur (i. e., in the near infrared and visible regions) are usually much more sensitive than detectors which operate in the region where fundamental CH vibrational transitions occur (i. e., in the mid infrared). However, the interpretation of experimental overtone spectra is complex, and the computational simulation of overtone spectra is challenging. Presented herein are the simulated vapour phase CH overtone stretching transitions in the nerve agent simulants trimethyl phosophate and triethyl phosophate. Spectral regions are simulated using the harmonically coupled an harmonic oscillator (HCAO) model. Data for HCAO calculations are obtained from ab initio calculations, without recourse to experimental data.