Temperature dependence of the Raman cross section and light absorption in cubic BaTiO3

The temperature dependence of the Raman spectrum in the cubic phase of BaTiO₃ is described. The cross section decreases when the temperature increases, which is contrary to a normal second order effect behaviour. The associated measurements of the optical absorption definitely prove that this variation is intrinsic. The anomalous Raman spectrum is related to the existence in the crystal of anisotropic fluctuation domains.     

Off-energy-shell effects in multiple scattering

The elastic scattering from a two-body bound system is investigated in order to determine what information about the nuclear structure and the projectile-nucleon interaction may be obtained at intermediate energies. Emphasis is placed on the kinematics and the importance of properly treating the overlapping potential region. The kinematics of the “fixed scatterer” and “impulse” approximations result in differences which are still significant at intermediate energies. As far as scattering information is concerned, the overlapping potential region is the interesting one since it requires explicit knowledge of the interaction. Our results suggest that for nucleon scattering at intermediate energies the corrections due to properly taking into account off-energy-shell effects are likely to be comparable with the contributions due to the short-range two-body correlations. The relevance of the above results to various models currently employed in analyzing high- and intermediate-energy nuclear scattering is also discussed.