Dynamic structure factor, friction and quasi-elastic scattering

C.A. CONDAT; J. JÄCKLE

Pittsburgh, PA (EE.UU.)

Conferencia; "March Meeting", American Physical Society; 1994

American Physical Society

The addition of a stochastic perturbation originates a quasi-elastic component in the neutron scattering cross section. To elucidate the genesis of this quasi-elastic component, we have investigated the influence of weak frictional forces on the dynamical structure factor S(k,w). Starting from suitable Langevin equations, we find an expression for S(k,w) in terms of the solution to a Fokker-Planck equation in energy-phase space. By a transformation of this equation, we obtain ordinary differential equations that describe the evolution of the probability density  along the energy axis for the various spectral regions. We can the find the scattered intensity by integration.