Design Considerations for a Portable Raman Probe Spectrometer for Field Forensics
Figure 7
Example of wavelength calibrated thin-film study of Semtex sample on a glass microscope slide using the Headwall/Andor prototype system, 6 mm 25 m slit, 200 lines/mm. The spectrum was recorded using 300 mW of 830 nm laser light. The Andor Newton CCD camera accumulated twenty, 1 s exposures. The wavenumber scale was calibrated using the decanoic acid spectrum shown in Figure 5. The upper trace is raw data, and the lower trace is baseline corrected utilizing a simple spline fit algorithm in Bruker’s OPUS software. The large offset between the Rayleigh peak (0 cm−1) and leftmost column of pixels (with extrapolated Raman shift of ~−630 cm−1) could potentially be exploited with V-notch-filter-based Raman probes to view the dominant anti-Stokes lines from lower order lattice vibrations. The edge filter of the Headwall/Andor prototype probe system does not allow us to access this low wavenumber region.
