Time resolved Raman spectroscopy for depth analysis of multi-layered mineral samples

Time resolved Raman spectroscopy (TRRS) can provide subsurface information from multi-layered samples of transparent and translucent evaporative and silicate minerals up to several centimetres thick. Depth information was obtained using 3-ps pulsed laser excitation at 720nm and a gated intensified charge-coupled device detector with stepwise increasing delay times. Blocks of different minerals were used as first, second or third layers, and Raman spectra from deeper layers could be detected through 10mm of translucent calcite and up to 40mm of transparent halite crystals. Measurements by conventional confocal Raman, as well as spatially offset Raman spectroscopy were also successful in distinguishing different mineral layers. This study establishes the great potential for the use of Raman spectroscopy in future planetary exploration, where TRRS could be used as a non-invasive tool for profiling the (sub-)surface at millimetre-depth resolution. Copyright (c) 2013 John Wiley & Sons, Ltd.