THERMAL SHIFT AND BROADENING OF THE 2E - 4A2 ZERO-PHONON LINES IN β-ALUMINA : CR3+ CRYSTALS G. Mariotto, M. Montagna et F. Rossi J. Phys. Colloques, 46 C7 (1985) C7-343-C7-347 DOI: 10.1051/jphyscol:1985762