Gated Raman spectroscopy: potential for fundamental and applied mineralogy

Using calcite as example, we demonstrate how a pulsed UV laser and time-resolved detection methods allow discrimination of Raman signals from strong luminescence background light. It is done in time domain and spectral domain. In time domain experiments, we use the fact that Raman scattering is produced almost instantaneously, whereas for emissions associated with luminescence, a minimum of hundreds of picoseconds elapse between electronic excitation and radiative decay. In the spectral domain, Raman peaks are very close to the UV excitation frequency whereas the luminescence is spectrally separated because of its larger Stokes shift compared to Raman. The UV gated Raman technique is a potential tool for remote sensing and online sorting of minerals.