Anomalous recoilless fraction of 30-Å-diameter FeOOH particles

Abstract
Investigation of a 30-Å iron oxyhydroxide catalyst by Mössbauer spectroscopy revealed that the recoilless fraction decreased dramatically with increasing temperature, becoming effectively zero at 50 K. This effect is explained on the basis of a combined effect of the recoil of the particle and the particle motion due to thermal agitation. The mean-square amplitude of particle motion is derived as a function of temperature. Application of uniaxial pressure to the sample or freezing the sample in carnuba wax increased the recoilless fraction markedly by enhancing the interparticle contact forces.