Influence of heavy-ion irradiation on the use of ruby as pressure calibrant

In recent years, samples pressurized in diamond anvil cells are being irradiated with energetic ion beams to investigate the response of solids to simultaneous exposure to ions and high pressure. The effects are numerous, e.g. inducing phase transitions far from their usual stability regime or creating and stabilizing phases that are normally not stable at ambient conditions, depending on the investigated material [1, 2]. A common method to calibrate the pressure in the DAC consists of adding a small ruby chip together with the actual sample into the pressure chamber [3]. The positions of the two luminescence lines R1 and R2 (694.28 nm and 692.85 nm) serve as pressure indicator [4]. However during the irradiation experiment, the ruby is exposed to the same radiation as the sample itself. Because the luminescence method is applied before and after irradiation to control the pressure inside the cell, the influence of ion radiation on the function of ruby as pressure calibrant had to be investigated.