Excitation

Noun

1. The act of exciting or putting in motion; the act of rousing up or awakening.
2. The act of producing excitement (stimulation); also, the excitement produced.
3. The activity produced in an organ, tissue, or part, such as a nerve cell, as a result of stimulation.
4. A transition of a nucleus, atom or molecule to an excited state by the absorption of a quantum of energy; the opposite of relaxation.