A square well atomic potential: NO2 treated iron-doped ZSM-5 zeolite

Treating iron-doped ZSM-5 zeolite with NO2 produced a complete change in th e parameters of its Fe-57 Mossbauer spectrum. The intensity of the absorpti on showed a dramatic decrease at 40-70 K with smooth, but anharmonic, behav ior above this temperature. The results can be interpreted in terms of the modification of the iron environment to form an approximately square-well p otential. This results in an asymmetric potential in which the iron becomes frozen in one region at low temperatures.