Raman spectroscopy applications of an imaging photomultiplier tube

A Raman spectroscopy system having an unprecedented combination of high sensitivity and low noise has been built incorporating an imaging (2-D) photomultiplier tube. The number of photons detected for a vibrational band approaches the theoretical limit set by the Raman cross section and experimental configuration. A detector dark count of 10(-4) counts/s/pixel is the major electronic source of noise. The spectrum of air reveals low concentration gas components, specifically (16)O(18)O and CO(2). Vibrational Raman spectra are obtained from solid samples as thin as 20 nm with low laser powers, e.g., 6.5 mW. The imaging photomultiplier yields 1-D (along the focused laser beam) Raman images of interfaces or concentration gradients.