Three-Dimensional Raman Tomographic Microspectroscopy: A Novel Imaging Technique

Chemical constituents and their spatial distributions in terrestrial and extraterrestrial samples may provide clues to their formation histories and secondary processes they were subjected to. Most analytical tools are either limited in imaging the interior of samples or they are destructive such that the sample is chemically modified. In this work, we have conducted three-dimensional Raman tomographic imaging experiments on both terrestrial and extraterrestrial samples. The in situ nondestructive analytical technique presented here provides spatial distribution of various chemical constituents from the interior of the samples with high spatial and depth resolution. Raman data were first collected from two-dimensional layers at the surface and at various depths inside the samples by means of confocal Raman imaging. Individual chemical distribution maps were generated for each layer, which were then stacked to form and visualize the three-dimensional distributions. In addition to three-dimensional distributions, Raman spectral information was also collected from each pixel within the measured areas, thus allowing us to also perform detailed spectral investigations of the samples.