Why does the effective area curve have bumps and edges?
The bumps and edges in the effective area curve appear because of resonance scattering and (or) absorption of X-rays which have energies near the M shell of the X-ray mirror’s reflecting material (iridium). The simplest Rutherford-Bohr model depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus. According to this model, the electrons can only circle in specific orbits. Each orbit is characterized by a certain discrete distance from the nucleus and specific energy. When the X-rays hit the reflecting material, the oscillating electric field of the electromagnetic radiation interacts with the electrons bound in an atom. There are two types of possible interactions: the radiation either will be scattered by these electrons, or it will be absorbed and excite photoelectrons. At certain energies the absorption increases dramatically and gives rise to an absorption edge. Each edge occurs when the energy of the incident
