ABNORMAL POPULATIONS AND VIBRONIC PROPERTIES OF THE ELECTRONIC LEVELS OF Fe2+ IONS IN ZnS : 57 Co MÖSSBAUER SOURCES C. Garcin, A. Gerard, P. Imbert et G. Jehanno J. Phys. Colloques, 40 C2 (1979) C2-413-C2-414 DOI: 10.1051/jphyscol:19792144