The Research Seminar Series in Archaeology and Environmental archaeology invites you to a seminar with Anne Christine Mirich, Umeå University, "Doing Things You’re Not Supposed to: Direct detection of the Mn-55 Paramagnetic Nucleus in Manganese Oxides".
Nuclear magnetic resonance (NMR) is an analytical technique that provides chemical structure information down to atomic resolution. NMR works by taking advantage of the dipole properties of the nucleus and measuring the signal as the nucleus re-aligns itself with an external magnetic field. Solid-state NMR (SSNMR) is an extension of the NMR technique that can be performed on materials such as soil, proteins, drugs, soaps, oils, polymers, glasses, and anything that is rigid enough to act like a solid. One limitation to the NMR technique is the direct detection of paramagnetic nuclei (atoms that contain loose electrons). Direct detection of a paramagnetic nucleus cannot be done because the fast relaxation induced by the unpaired electrons causes the signal to decay faster than the NMR timescale (which operates in milliseconds). This work overcomes the paramagnetic and reporter nuclei problem in manganese oxides by taking advantage of the antiferromagnetic properties of manganese oxides.
For this work, a new, fast pulse sequence was created to capture antiferromagnetic areas in manganese oxides. Due to this fast pulse sequence, direct observation of the Mn-55 nucleus was accomplished. Results show that the polymorphs of MnO2 (13 different polymorphs) are distinct, allowing the different phases to be characterized via SSNMR. Other polyoxides (MnO, Mn2O3, Mn3O4) shows that manganese oxides with different oxidation states can also be captured. This work complements other analytical techniques like X-ray diffraction (XRD) and Raman, which are used for phase identification. Other areas of research that could benefit from this technique include materials that may not always be well characterized by XRD (amorphous phases), catalysts, batteries, and mineralogy.
The Research Seminar Series in Archaeology and Environmental Archaeology presents and discusses current research in archaeology and environmental archaeology.
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