MÖSSBAUER AND OPTICAL ABSORPTION EXPERIMENT ON 151Eu ATOMS ISOLATED IN AN ARGON MATRIX F. J. LITTERST, A. SCHICHL, M. JAKOB et H. MICKLITZ J. Phys. Colloques, 37 C6 (1976) C6-59-C6-60 DOI: 10.1051/jphyscol:1976614