A technique used to decouple the motion of nuclei and electrons (i.e., separate the variables corresponding to the nuclear and electronic coordinates in the Schr dinger equation associated to the molecular Hamiltonian). It is based on the fact that typical electronic velocities far exceed those of nuclei.

When the frequency of emitted photon is equal or larger than the exciting (absorbed) photon. The extra energy can be contributed from phonon absorption (lattice vibration) or from molecular kinetic energy.

One of two principal processes for relaxation of inner-shell electron vacancy in an excited or ionized atom. It is a two-electron process in which an electron makes a discrete transition from a less bound shell to the vacant but tightly bound electron shell. The energy gained in this process is transferred, by means of electron static interaction, to another bound electron, which then escapes from the atom (called the Auger electron).

The motion of electrons in ultrasmall (highly confined) regions in semiconductor structures at very high electric field with velocities much higher than their equilibrium thermal velocity. The ballistic electrons are not subjected to scattering, so they can move with ultrahigh velocity. The ballistic transport is determined by the electronic structure of the semiconductor and is different for different semiconductors and this allows ultrafast devices. Ballistic transport is also extended to other microscale energy carriers, indicating transport with no scattering.