Swift heavy ion induced amorphization in zircon as part of various experimental series

To investigate the irradiation-induced structural damage in zircon, that may potentially influence dating methods, we exposed zircon samples to swift heavy ions in two different experimental series. To quantify the impact of increasing irradiation, the first series involved irradiation with gold ions (Au⁷⁹⁺) at an energy of 8.6 MeV/u, with target fluences of 1e¹¹, 2e¹¹, 5e¹¹, 1e¹², and 5e¹² ions/cm² at atmospheric pressure and 25 °C on disc-sliced zircon. Since the second series of experiments focused on the influence of pressure as an additional factor, we used a Paris-Edinburgh press combined with a modified (toroidal) large-volume diamond anvil cell (DAC) with diamond windows, which enabled the irradiation of entire zircon grain samples of larger sizes, approximately 2-3 mm. One of these samples was irradiated with uranium ions (U⁹²⁺) at an energy of 480 MeV/u and a pressure of 1.5 GPa at 25 °C.

Using confocal Raman spectroscopy, the focus was on the changes in the FWHM of the ν3(SiO₄) Raman band at approximately 1008 cm⁻¹ as an indicator of structural damage. The peak position exhibited shifts towards lower wavenumbers, and increased peak widths correlated with increasing fluence, showing a strong relationship between ion irradiation and the degree of amorphization. Maps of the samples of the second series show a linear shift of up to 4 cm⁻¹ that is localized exclusively along the irradiation path. However, to more accurately determine the influence of pressure, further analytical methods, such as TEM and EBSD, are still necessary.