[1] P Adolf, S Karl. Gems & Gemology, 1, 17(1999).

[5] G Pezzotti, W Zhu. Journal of Raman Spectroscopy, 42, 2015(2011).

[6] R S Krishnan, S P S Porto. The Journal of Chemical Physics, 3, 1009(1967).

[7] P Tarte. Spectrochimica Acta Part A: Molecular Spectroscopy, 23, 2127(1967).

[9] A R Moon, M R Phillips. Journal of Physics and Chemistry of Solids, 52, 1087(1991).

[10] A R Moon, M R Phillips. Journal of the American Ceramic Society, 77, 356(1994).

[11] E Balan. European Journal of Mineralogy, 32, 457(2020).

[12] M Digne et al. Journal of Physical Chemistry B, 106, 5155(2002).

[14] H Harder, G Lehman. American Mineralogist, 98(1970).

[15] B C Bhatt, B C Dhabekar, P S Page et al. Journal of Luminescence, 130, 882(2010).