MÖSSBAUER STUDIES OF THE ACTIVATION OF AMMONIA SYNTHESIS CATALYSTS B. S. CLAUSEN, S. MØRUP, H. TOPSØE, R. CANDIA, E. J. JENSEN, A. BARANSKI and A. PATTEK J. Phys. Colloques, 37 C6 (1976) C6-245-C6-248 DOI: 10.1051/jphyscol:1976649