Raman spectrometry of explosives with a no-moving-parts fiber coupled spectrometer: A comparison of excitation wavelength

In this study Stokes Raman spectra measured with 785 and 830 nm excitation, as well as 1064 nm anti-Stokes Raman spectra, of 23 explosive materials were obtained using fiber-optic sampling and a no-moving parts spectrograph. By using a silicon charge-coupled device (CCD) detector, 830 nm Stokes Raman spectra were collected over the range 100-2400 cm−1. 830 nm excitation offers slightly better fluorescence rejection than 785 nm, which is key for the analysis of some fluorescent explosives. Even with a high-powered 1064 nm laser, anti-Stokes measurements did not yield spectra of as high quality as 785 and 830 nm Stokes Raman measurements. Fourier transform (FT)-Raman remains the preferred method for fluorescence-free analysis of these explosive materials in the laboratory, but 830 nm excitation is preferred for a field-portable instrument.