Resonance-Enhanced Raman Spectroscopy on Explosives Vapor at Standoff Distances
Figure 7
Apparent resonance enhancement of the Raman signal compared to the Raman cross section at 532 nm for (a) the 1347 cm−1 line in 2,4-DNT at different DNT concentrations and (b) the 1358 cm−1 line in 2,4,6-TNT at different TNT concentrations. The wavelength of the incident light was 248 nm, and a 248 nm long-pass filter was used in both measurements. The enhancement varies with concentration due to the absorption effects. Note that the maximum enhancement for the higher concentrations of DNT is found at longer wavelengths than 248 nm, whereas it is close to the wavelength giving maximum enhancement for TNT at 341 ppm.
