Effect of Pressure on the Spectra of Olivine and Garnet

Abstract

The effect of pressure has been measured on the absorption edge of olivine and on the Fe⁺⁺ peak of garnet to over 150 000 atmos. The absorption edge of olivine shifts red by about 9% of the gap in this pressure range. The Fe⁺⁺ peak in garnet shifts to higher energies by 700 cm⁻¹ in 170 000 atmos, due to increased splitting of the d levels by the ligand field. This is consistent with previous experimental work on transition metals, and with available theory. The temperature coefficient of the absorption edge of olivine was also measured at atmospheric pressure to 327°C. It exhibited a linear red shift of 4.21×10⁻⁴ ev/°C over this range.