ABSTRACT
Photon emission is, therefore, a fundamental process and a major goal of this chapter is to explain the concept of induced and spontaneous emission. It deals with transmission and reflection of a free particle at a potential barrier. The chapter helps the reader to understand quantitatively very diverse topics: how atoms can wander about the grain surface by way of tunneling through a potential barrier; how protons can fuse to deuteron in the interior of the Sun; how electrons are energetically arranged in white dwarfs; or how electronic bands appear in crystallized grains. It reviews the solution of the time-independent Schrödinger equation for the undamped free linear harmonic oscillator.
