Excited State

Excited State

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.

Read more about Excited State:  Atomic Excitation, Perturbed Gas Excitation, Calculation of Excited States, Reaction

Famous quotes containing the words excited and/or state:

    The existence of good bad literature—the fact that one can be amused or excited or even moved by a book that one’s intellect simply refuses to take seriously—is a reminder that art is not the same thing as cerebration.
    George Orwell (1903–1950)

    Think of the importance of Friendship in the education of men.... It will make a man honest; it will make him a hero; it will make him a saint. It is the state of the just dealing with the just, the magnanimous with the magnanimous, the sincere with the sincere, man with man.
    Henry David Thoreau (1817–1862)