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| Book/Report | FZJ-2018-01599 |
1981
Kernforschungsanlage Jülich, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/17561
Report No.: Juel-1726
Abstract: The Langevin-equation is used for rotational motion. The rotational Langevin-equation is solved for rotators with one, two and three degrees of freedom by numerical methods. From the solutions correlation functions are extracted. The calculated correlation functions are chosen with respect to applications in neutron scattering. In the case with one and two rotational degrees of freedom the Langevin-results are compared with earlier results obtained with different methods. It is found that in certain parameter ranges other models are able to describe the problem. If the rotational barrier height is larger than about 8 times the thermal energy the harmonicapproximation to the potential give good results. In the case of three rotational degrees of freedom the dynamics of the rotational motion of the moleeule is studied in some detail. It is found that the jump models are only reasonable good for very large barrier heights. For smaller barrier heights (< 5 k$_{B}$T) the motion is much more diffusive than jump like. Without a fitting parameter the width of the neutron scattering law and activation energy are calculated. They both agree very weil with experimental results.
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