We have recently acquired a new-generation, state-of-the art, Raman spectrometer with imaging capability and multi-wavelength excitation. A Raman imaging system will provide molecular maps (similar to the element map provided by an Electron Microprobe). It will collect a Raman image cube from a sample, then to generate the map of minerals, molecular species (H2O/OH), and chemical bonds (e.g., C-H, N-H, C-O, C-C, etc). The spatial distributions and spatial correlations of various species will reveal the evidences of past physic-chemical-biologic processes, as well as the genetic relationships among the different species. A Raman system with multiple excitation laser wavelengths is capable to study a wide variety of materials. A different excitation wavelength will affect the Raman cross sections of materials; sometimes will enhance Raman signals by inducing Raman resonance effect. More importantly, it will help to overcome the interference of fluorescence generated by some targets.
Raman imaging system – Renishaw InVia
• Five laser wavelengths for Raman excitation from UV to NIR: 325 nm, 442 nm, 532 nm 633 nm, and 785 nm;
• A Raman spectrometer with high spectral resolution (~ 1 cm-1) and wide spectral range (50- 4000 cm-1) for all five excitation wavelengths;
• A microscope with high accuracy moving stage and a wide range of microscopic objectives, 5x, 10x, 20xLWD, 50x, 50xLWD, 100xLWD;
• A microscope with cross-polarization for transmitted light and reflected light for visualization and B/W mosaic imaging;
• Three ways to take Raman spectra and five ways to take Raman images;
• The highest special resolution are 200-300 nm in X-Y and 500 nm in Z direction.
• Solid samples — rock chip (less than 1 kg, less than 5 cm height), soils or powders, single gains, films, etc, and no sample preparations are needed. Double-side flat cut surfaces would be preferred for taking Raman images.
• Thin or thick sections — Super-glue is better than epoxy for thin section; the cover slide and carbon coating (if there is any) should be removed.
• Liquid samples — in glass bottle, glass capillary, liquid cell, or in petri dish.
Contact: Prof. Alian Wang
Acknowledgement: the funds for purchasing this top-level Raman Imaging system are from NASA Mars Fundamental Research program — Planetary Major Equipment program, and from Washington University in St. Louis (School of Art & Science, Dept. Earth and Planetary Sciences, and McDonnell Center for Space Sciences).