Scattering exchange effects

It has been widely recognized that the Ught scattering technique yields essential information on a dynamic mechanism of ferroelectric phase transition because it clearly resolves the dynamics of the ferroelectric soft mode that drives the phase transition. Quantum paraelectricity is caused by the non-freezing of the soft mode. Therefore, the isotope-exchange effect on the soft mode is the key to elucidating the scenario of isotopically induced ferroelectricity. 

Temkin, A. (1957). Polarization and exchange effects in the scattering of electrons from atoms with applications to oxygen. Phys. Rev. 107 1004-1012. 

It can be seen that electron—photon coincidence experiments with polarised electrons permit the investigation of spin effects in electron impact excitation of atoms at the most fundamental level. It can lead to direct information on both exchange effects and spin—orbit effects in the excitation mechanism. The information on the population of the magnetic sublevels can be visualised by charge-cloud distributions. These can tilt significantly out of the scattering plane for incident electrons transversely polarised in the scattering plane. 

In scattering on a pair of identical particles in H2, D2, H2O, D2O and close pairs of protons or deuterons in molecules or metal hydrides, the quantum exchange effect must be taken into account by antisymmetrization of the initial state 4 i,... 

This is shown in Fig. 22.8, which in addition contains two points from electron Compton scattering on hydrogen molecules. Those were obtained by Cooper et al. [16] and have been introduced at 37° (which corresponds to their -values) on the 0-scale. Their positions support the theory given above (which should be applicable also to electron Compton scattering), a 31 % anomaly for H2 and no anomaly for HD molecules (no quantum exchange effect). 

Until very recently, however, the same could not be said for reactive systems, which we define to be systems in which the nuclear wave function satisfies scattering boundary conditions. It was understood that, as in a bound system, the nuclear wave function of a reactive system must encircle the Cl if nontrivial GP effects are to appear in any observables [6]. Mead showed how to predict such effects in the special case that the encirclement is produced by the requirements of particle-exchange symmetry [14]. However, little was known about the effect of the GP when the encirclement is produced by reaction paths that loop around the CL... 

---