Spectroscopic properties of the rubidium and cesium aluminum double molybdate crystals

Infrared, Raman, electron absorption, excitation and emission spectra were measured for RbCrxAl1−x(MoO4)2 and CsCrxAl1−x(MoO4)2 crystals (x=0–2%) at the temperatures ranging from 7 to 300 K. A very rich vibronic structure of the emission band was explained and assigned to the respective vibrational modes. One Cr3+ center characterized by 2.35 ms lifetimes for rubidium derivative and 1.3 ms for cesium one at 7 K for the 2E→4A2 transition was identified for both crystals. The local structure of the Cr3+ surrounding is discussed in terms of the spectroscopic results and the crystal field parameters are derived for both materials.