Imaging of nano-crystals: theoretical modeling and experimental investigation

• Grant number: 09/53150-4
• Support type: Scholarships abroad - Research
• Effective date (Start): March 01, 2010
• Effective date (End): August 31, 2010
• Field of knowledge: Physical Sciences and Mathematics - Physics
• Principal researcher: Antonio Rubens Britto de Castro
• Grantee: Antonio Rubens Britto de Castro
• Host: Thomas Moller
• Home Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Research place: Technical University of Berlin (TU), Germany

Abstract

We are concerned with the description of imaging experiments using light scattering from a single femtosecond X-ray laser pulse incident on a single nanocrystal (or set of a few single nanocrystals). Following our successful discussion and application of the scalar scattering model for arbitrary tenuous scatterers, we want to explore vector models for situations of non-uniform non-tenuous scatterers of non-spherical shape, which depart little and not so little from uniform and spherical. We will consider (a) solutions of the 3-dim Helmholtz equation in spheroidal coordinates, (b) techniques of vector diffraction theory, (c) perturbations of the exact Mie theory. In these macroscopic electro-dynamical calculations the complex refractive index n is taken as given. However, it depends on the electron density and the energy band structure of the atoms in the nanocrystal, which will be changing during the X-ray pulse. The recorded scattering image represents therefore some time average of evolving cross-sections, which depend on time-changing optical functions. We intend to make simple estimates of these time-dependent optical functions. Experimental data are obtained at the X-ray free-electron-laser in Hamburg. (AU)