Evolution of x-ray emission spectra with pressure. All spectra are shifted so that the main emission line is at 7,058 eV. A low-spin spectrum of Al-free perovskite is shown for reference (15). (Upper) Evolution of x-ray emission spectra of the Al-bearing perovskite sample in the satellite region from 7,030 to 7,050 eV, during compression. (Lower) Evolution of x-ray emission spectra of the Al-free perovskite sample in the satellite region from 7,030 to 7,050 eV, during compression (circles) and decompression (squares, 40 GPa). The spectrum at 40 GPa is measured during decompression, and shows the reversibility of the observed intensity changes.