Heavy-ion irradiation on crystallographically oriented cordierite and the conversion of molecular CO2 to CO: a Raman spectroscopic study |
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| Authors: | Christian Weikusat Ronald Miletich Ulrich A Glasmacher Christina Trautmann Reinhard Neumann |
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| Institution: | (1) Institute of Earth Sciences, University of Heidelberg, 69210 Heidelberg, Germany;(2) GSI Helmholtzzentrum, 64291 Darmstadt, Germany |
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| Abstract: | Crystallographically oriented sections of natural gemstone quality cordierite single-crystals have been irradiated with swift
heavy ions of GeV energy and various fluences. Irradiation effects on the crystal lattice were investigated by means of Raman
spectroscopy. Raman line scans along the trajectory of the ions reveal a close correlation of beam parameters (such as fluence
and energy loss dE/dx along the ion path) to strain due to associated changes in lattice dimensions and defect concentration. The luminescence
background also scales with the ion fluence and suggests the formation of point defects, which could also account for the
macroscopically observable colouration of the irradiated samples. In addition, changes in the amount and nature of volatile
species inside the structural channels are observed. They also scale with dE/dx and confirm the previously postulated irradiation-induced conversion of CO2 to CO. Irradiations along the crystallographic a-, b- and c-axis reveal no significant anisotropy effect with respect to lattice alterations. The polarisation characteristics of the
Raman-active modes confirm the preferred molecular alignment of CO and CO2 along the a-axis direction. |
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