Photon Systems’ technology is built around the many benefits of Rayleigh scattering, resonance Raman and Raman scattering, and fluorescence and phosphorescence detection when excitation occurs in the deep UV below 250 nm. The core technology of Photon Systems has been an array of deep UV lasers and incoherent sources and optics compatible with instrumentation in the deep UV. These deep UV sources and optics are the enabling technology for a wide range of instruments for detection of trace amounts of chemical and biological materials on surfaces, in liquids, or in air.
Trace concentrations are typically in the femtogram range with concentrations in the picograms per cm2. Microbial detection is down to a fraction of a single bacterial spore, or viruses. Photon Systems has additionally developed advanced detection electronics offering over 7 decades of linear dynamic range down to near single photon or electron counting, plus software and on-board computing for chemometric analysis and data processing, library matching, instrument communication, and much more.
A broad perspective of the relationship between Raman and native fluorescence spectral regions is illustrated below, along with the emission wavelength of typical lasers and the spectral range of their Raman range. It is commonly accepted practice to employ near IR excitation to avoid fluorescence from target molecules or surrounding materials within the exposure volume, but with excitation even as high as 830 nm, it has been shown that a large fraction of materials investigated exhibit major fluorescence interference¹ to the point that it completely obscures Raman emissions. Moving further into the IR, to 1064 nm or longer, further reduces the Raman scatter cross-sections in increased penetration of excitation energy, producing a wider range of interferents or confusants in the spectra, and eliminates the ability to detect fluorescence emissions from many low phenyl ring materials.
¹ Frosch, T., et.al. UV Raman Imaging, A promising tool. Anal. Chem. Vol.79, No.3, (Feb. 1, 2007)
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