Memory scattering

Three common types of electrooptic effects are illustrated in Figure 8 i.e, quadratic and linear birefringence and memory scattering. Also included in the figure is a typical setup required for generating each effect along with the observed behavior shown in terms of light intensity output (I) as a function of electric field (E). 

After some typical time, r, the electron will scatter off a lattice imperfection. This imperfection might be a lattice vibration or an impurity atom. If one assumes that no memory of the event resides after the scattering... 

Static defects scatter elastically the charge carriers. Electrons do not loose memory of the phase contained in their wave function and thus propagate through the sample in a coherent way. By contrast, electron-phonon or electron-electron collisions are inelastic and generally destroy the phase coherence. The resulting inelastic mean free path, Li , which is the distance that an electron travels between two inelastic collisions, is generally equal to the phase coherence length, the distance that an electron travels before its initial phase is destroyed ... 

De Santis A., Nardone M., Sampoli M. Light scattering orientational memory functions for fluid N2 at moderate densities, Mol. Phys. 40, 1185-96 (1980). 

In this chapter, we also discussed several schemes that allow for the computation of scalar observables without explicit construction and storage of the eigenvectors. This is important not only numerically for minimizing the core memory requirement but also conceptually because such a strategy is reminiscent of the experimental measurement, which almost never measures the wave function explicitly. Both the Lanczos and the Chebyshev recursion-based methods for this purpose have been developed and applied to both bound-state and scattering problems by various groups. 

In addition to the above three effects, there are two others i.e, memory birefringence and depolarization scattering, which exist in the PLZT materials and have been proposed for device applications. These are described in reference 5. 

When I wake up at night with ideas, I jot the ideas on a pad so that I can recall them in the morning. Proust also woke with his head flooded with memories and ideas. He sometimes awoke unaware of where he was or even who he was. He seemed to transcend space and time as he remembered events of his youth or conjured poetic visions of his great-aunt s house in Combray or his trips to Paris, Doncieres, and Venice. As you will see through anecdotes scattered throughout this book, his realities are often not ordinary realities to which you and I have ready access. 

Physically this description corresponds to putting an atom (mass M) in an external time-dependent harmonic potential (frequency co0). The potential relaxes exponentially in time (time constant l/x0) so that eventually the atom experiences only a frictional force. Compared with other models2 which have been proposed for neutron scattering calculation, the present model treats oscillatory and diffusive motions of an atom in terms of a single equation. Both types of motion are governed by the shape of the potential and the manner in which it decays. The model yields the same velocity auto-correlation function v /(r) as that obtained by Berne, Boon, and Rice2 using the memory function approach. 

The form displayed in eq. (2-40) implies that the ratios of the amplitudes for scattering into different exit channels are independent of the entrance channel. This, of course, will only be true if the resonance is long lived, so that memory of the initial state can be lost. Note that Aga is a symmetric function, which is a consequence of time-reversal invariance. Note also that, within the approximations used, the phase shift associated with a given channel is just the elastic scattering phase shift for that channel. Finally, the partial widths are proportional to the probability of decay from channel fi. Equation (2-41) is, then, merely a statement that the total probability of decay from channel is the sum of the probabilities of decay into individual channels. 

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