Anandh Subramaniam & Kantesh Balani MATERIALS SCIENCE & ENGINEERING Anandh Subramaniam & Kantesh Balani Materials Science and Engineering (MSE) Indian Institute of Technology, Kanpur- 208016 Email: anandh@iitk.ac.in, URL: home.iitk.ac.in/~anandh AN INTRODUCTORY E-BOOK Part of http://home.iitk.ac.in/~anandh/E-book.htm A Learner’s Guide

2 Incoherent Scattering (Compton modified) From loosely bound charges Coherently scattered X-rays contribute to X-ray diffraction. Incoherently scattered X-rays darken the background and are not useful from a XRD point of view. In Compton modified scattering, X-rays are incoherently scattered on the interaction with loosely bound electrons in the material. This leads to a increase in the wavelength of the X-rays and a decrease in the energy. Here the particle picture of the electron & photon comes handy Electron knocked aside 2 No fixed phase relation between the incident and scattered waves Incoherent  does not contribute to diffraction. (Darkens the background of the diffraction patterns).

Fluorescent X-rays Energy levels This signal is produced akin to the way the original X-ray beam was produced; just that the input now is not electrons but X-rays. The fluorescent X-rays can be used for spectroscopy (X-ray Fluorescence Spectroscopy, XRF). However, in an XRD experiment it is an nuisance and leads to an increase in the background level. E.g. Fe sample studied with Cu k radiation leads to fluorescence. Knocked out electron from inner shell Vacuum Energy levels Characteristic X-rays (Fluorescent X-rays) (10−16s later  seems like scattering!) Nucleus