Influence of low-symmetry component of crystal field on gemstones colors: Cr3+ in ruby and emerald

摘要

The origin of difference in the colors of two gemstones - red ruby Al2O3:Cr3+ and green emerald Be3Al2(SiO3)(6): Cr3+ is explained by analyzing the crystal field effects. It is shown that the stronger crystal field in ruby and the significantly greater low-symmetry component of crystal field in emerald are the main sources of the observed color difference. Calculated energy levels of the Cr3+ ions in both materials agree well with the experimental results.