In quantum mechanicsan Into the excited state of a system such as an atommolecule 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. 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 Into the excited atom being raised to an excited state. The lifetime of a system in an excited state is usually short: 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. A simple example of this concept comes by considering the hydrogen atom.
The ground state of the hydrogen atom corresponds to having the atom's single electron in the lowest possible orbit that is, the spherically symmetric Into the excited 1s " wave-functionwhich, so far, has demonstrated to have the lowest possible quantum numbers.
By giving the atom additional energy for example, by the absorption of a photon of an appropriate energythe Into the excited is able to move into an excited state one with one or more quantum numbers greater than the minimum possible.
If the photon has too much energy, the electron will cease to be bound to the atom, and the atom will become ionized. After excitation the atom may return to the ground state or a lower excited state, by emitting a photon with a Into the excited energy. Emission of photons from atoms in various excited states leads to an electromagnetic spectrum showing a series of characteristic emission lines including, in the case of the hydrogen atom, the Lyman, Balmer, Paschen and Brackett series.
An atom in a high excited state is termed a Rydberg atom. A system of highly excited atoms can form a long-lived condensed excited state e.