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 easily, 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 down to 4.6 K, which shows that they are more distant from the magnetically ordered oxide substrate. Additionally, their thermal vibration amplitudes 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-Karyagin effect to be seen. Thermal vibration amplitudes of Sn(II) are then found to be greater in the plane of the three neighbouring sulfur atoms than in the perpendicular direction. Copyright (C) 1996 Elsevier Science Ltd