Applications

Abstract

Optical spectra are the principal means to experimentally obtain the band gaps and energies for interband transitions. For isolated atoms and ions the absorption and emission spectra are known to be extremely sharp. Thus, absorption and emission energies for atoms can be determined with great accuracy. The same is basically true for molecular spectra. In contrast to this, the optical spectra of solids are rather broad. This stems from the high particle density in solids and from the interatomic interactions which split the atomic levels into quasicontinuous bands. The latter extend through the three-dimensional momentum space of a Brillouin zone.