ABSTRACT
This chapter considers the response of electrons in solids to both longitudinal and transverse external probes. It discusses characteristic energy-loss experiments and optical experiments. The chapter provides a brief review of some of the properties of Bloch wave-matrix elements and excitation energies which are relevant for purposes. It describes the remark that a class of solids for which interband effects are surely important in determining plasmon behavior are the transition metals and those lying just beyond them. The chapter examines the probability per unit time for the processes in which a photon of the incident wave is absorbed, while a new photon is created in a different state; the state of the electron system undergoes a quantum shift from the ground state. It focuses on the quantum treatment of the basic Hamiltonian before going on to a comparison of theory and experiment.
