An excited state is any energy state of an electron or atom higher than the ground state, reached when the atom absorbs energy. An atom in an excited state is unstable and tends to return to a lower state, releasing the extra energy, often as a photon of light. The wavelengths emitted in this way give rise to an element's line spectrum.

激发态是电子或原子高于基态的任何能量状态,在原子吸收能量时达到。处于激发态的原子不稳定,往往返回较低状态,并释放多余的能量,常以光子形式放出。以此方式放出的波长形成了元素的线状光谱。