Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state.
In quantum mechanics an excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum). The temperature of a group of particles is indicative of the level of excitation (with the notable exception of systems that exhibit Negative temperature).
The lifetime of a system in an excited state is usually short: spontaneous or induced emission of a quantum of energy (such as a photon or a phonon) usually occurs shortly after the system is promoted to the excited state, returning the system to a state with lower energy (a less excited state or the ground state). This return to a lower energy level is often loosely described as decay and is the inverse of excitation.
Long-lived excited states are often called metastable. Long-lived nuclear isomers and singlet oxygen are two examples of this.
Other articles related to "excited state, state, excited, excited states":
... Photobleaching can occur either from excitation into an even higher excited state, or from excitation in the triplet state ... To prevent the excitation of an excited electron into another, higher excited state, the energy of the photon needed to trigger the alternative emission should not ... emission, and not cause the electron to be excited to another, higher energy state ...
... consequence is reaction of the atom in the excited state, as in photochemistry ... Excited states give rise to chemical reaction ...
... excitation is the movement of an electron to a higher energy state ... When an excited electron falls back to a lower energy state again, it is called electron relaxation ... for energy level which is often associated with an atom being excited to an excited state ...
... of another chemical species can accelerate the decay rate of a chemical in its excited state ... A is one chemical species, Q is another (known as a quencher) and * designates an excited state ... is the quencher rate coefficient, is the lifetime of the emissive excited state of A, without a quencher present and is the concentration of the quencher ...
... The phase qubit is operated in the zero-voltage state, with ... Transitions from the zero voltage state to the voltage state were measured by monitoring the voltage across the junction ... several quantized energy levels, with the lowest (ground to first excited state) transition at an energy, but the higher energy transitions (first to second excited state, second to third excited state ...
Famous quotes containing the words state and/or excited:
“The law of nature is alternation for evermore. Each electrical state superinduces the opposite. The soul environs itself with friends, that it may enter into a grander self-acquaintance or solitude; and it goes alone for a season, that it may exalt its conversation or society.”
—Ralph Waldo Emerson (18031882)
“Yet always when I look death in the face,
When I clamber to the heights of sleep,
Or when I grow excited with wine,
Suddenly I meet your face.”
—William Butler Yeats (18651939)