When temperature of an atom increases or energy is provided to atoms, they get excited. When electrons in atom moves from lower orbit to higher orbits, they are called as excited electrons. Excited electrons stay at their state of excitation for 10-8 sec. After this period they come back to their ground state by releasing energy. Electrons release energy in the form of photons or radiations. Atoms can also be excited by using photon and charged particles. Laser light is also produced by excitation of atoms. Moreover, atom releases-rays when a beam of electrons is incident on a heavy nucleus.
