METHOD OF SPECTROSCOPY

摘要

A spectroscopy method and apparatus comprises an excitation source arranged to excite a vibrational mode of a sample and provide multi-dimensional spectral information by varying the excitation in a time or frequency domain. A parameter of a further excitation source or of the sample is controlled so as to provide coherence spectroscopy by ensuring that a non-resonant local oscillator field generated in the sample dominates a homodyne signal generated in the sample. As a result heterodyne detection is achieved in a manner allowing an output signal linearly dependent upon concentration providing improved sensitivity. In an alternative embodiment where heterodyning is not used, an ultraviolet or visible excitation excites an electronic resonance, whereafter fluorescence is measured.