Neutron and infrared study of the dynamical behaviour of methane in NaA zeolite

Abstract

The study by infrared and neutron spectroscopy of the dynamical behaviour of one methane molecule adsorbed in the synthetic zeolite NaA shows several interesting features : i) the molecule remains for a time longer than 10 -9 s in the same cavity, ii) whereas at room temperature it moves within the entire volume of the cavity, when the temperature decreases its trajectory gets closer and closer to the walls with a longer trapping time in definite sites. At 4 K the molecule is completely trapped in these sites. iii) From the correlation time of this motion (10-11 s at 240 K) and the life time of the v1 internal vibration we obtain an activation energy of 700 K