LOCAL ENVIRONMENT AND DYNAMIC CHARACTERISTICS OF THE SN-119(II) AND SN(IV) MOSSBAUER PROBES ON THE SURFACE OF CR2O3 EXPOSED TO HYDROGEN-SULFIDE ATMOSPHERE

Tin dopant located on the surface of Cr2O3 crystallites interacts easi ly, at room temperature, with adsorbed H2S molecules. Contrary to the initial oxygen-surrounded tin species, the resulting Sn(II) and Sn(IV) sulfur-surrounded entities exhibit no spin polarization, at least dow n to 4.6 K, which shows that they are more distant from the magnetical ly ordered oxide substrate. Additionally, their thermal vibration ampl itudes are greater than in oxygen-surrounding, which denotes a weaker bonding of the tin within the H2S adsorbed layer. Moreover, for Sn(II) , sufficiently large quadrupole splitting allows the Goldanski-Karyagi n effect to be seen. Thermal vibration amplitudes of Sn(II) are then f ound to be greater in the plane of the three neighbouring sulfur atoms than in the perpendicular direction. Copyright (C) 1996 Elsevier Scie nce Ltd