Paramagnetic resonance spectrum of Cr+++ in emerald

Paramagnetic resonance for the Cr
⁺⁺⁺
ion in emerald has been observed at X-band (8.2 to 12.4 kmc), K-band (18 to 26.5 kmc) and M-band (50 to 75 kmc). From spectra observed at these frequencies, the spectroscopic splitting factors g
$$ , g$$ and D have been determined. The large value of D observed suggests the possible use of emerald as an active material in relatively high microwave-frequency solid-state masers.