Raman Spectroscopy (RS) is a vibrational spectroscopic analysis technique that produces information about the chemical structure, phase, crystallinity, and molecular composition of a material. RS uses one or more lasers in the ultra-violet to the mid-infrared wavelength range, the selection of which depending on the required experimental capabilities.
The Archaeometry Laboratory recently acquired a Bruker Bravo™ handheld Raman spectrometer. The instrument is equipped with two laser diodes (excitation wavelengths of 785 nm and 852 nm) and can operate at a maximum (combined) laser output of 100 mW and a spot size of ~1 mm. It records signal intensity data at a spectral range of 300 - 3200 cm-1 at a resolution of 10-12 cm-1. One unique capability of the dual-laser system is sequentially shifted excitation (SSE), a technique that minimizes the effects of sample fluorescence on the resulting spectrum. It does this by operating the two lasers at sequentially shifted wavelengths (< 1 nm), during which the fluorescence bands and unwanted spectral artifacts remain at fixed positions in the spectrum while the positions of the Raman bands will shift slightly in response to the minor variations in excitation wavelength. During a single measurement, the instrument collects six independent interferograms that are subsequently compiled into a single calculated spectrum. This capacity enables the instrument software to then identify and subtract the unwanted fluorescence bands, resulting in significantly reduced spectral interferences. This capability is especially desirable for the analysis of materials with fluorescence-inducing components, which are commonly encountered in archaeomaterials analysis. See Jehlička and Culka (2021) and Culka and Jelička (2019) and for detailed evaluations of Bravo’s SSE functionality.
One major advantage for archaeological and geological applications is the portability of the handheld Bruker Bravo. This allows for the non-invasive analysis of materials in situ at remote field sites and museums. When coupled with our portable XRF instruments, it creates a powerful toolkit for the elemental and molecular characterization of materials.
Per-sample costs for Raman spectroscopic analysis ranges from $25-$50 per sample depending on the matrix and project needs. To obtain a quote for a prospective project please contact Dr. Brandi MacDonald for consultation.