Temperature Spatially Offset Raman Spectroscopy (T-SORS): Subsurface Chemically Specific Measurement of Temperature in Turbid Media Using Anti-Stokes Spatially Offset Raman Spectroscopy

Here we propose and demonstrate a new analytical method for the noninvasive measurement of subsurface temperatures within diffusely scattering (turbid) media in combination with high chemical selectivity. The method is based upon the first combination of Stokes/anti-Stokes light scattering measurements and the recently developed spatially offset Raman spectroscopy (SORS). This approach has been conceptually demonstrated by measuring material-specific temperatures within a turbid sublayer of poly(tetrafluoro ethylene) (PTFE) through a highly diffusely scattering overlayer of poly(oxymethylene) POM (3 mm thick). Root-mean-square errors (RMSEs) of 0.16-0.71 degrees C were achieved when measuring temperatures over ranges between 24 and 45 degrees C. This unique capability complements the array of existing, predominantly surface-based, temperature measurement techniques. It paves the way for a wide range of topical applications including subsurface, chemically specific, noninvasive temperature measurements within translucent media including the human body, subsurface monitoring of chemical or catalytic processes in manufacture quality and process control, and research.