Excitation function is a term used in nuclear physics

Nuclear physics

Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...

 to describe a graphical plot of the yield of a radionuclide or reaction channel as a function of the bombarding projectile energy or the calculated excitation energy of the compound nucleus.

The excitation function typically resembles a Gaussian bell curve

Bell curve

Bell curve can refer to:* A Gaussian function, a specific kind of function whose graph is a bell-shaped curve* Normal distribution, whose density function is a Gaussian function...

. Mathematically, it is described as a Breit-Wigner function, owing to the resonant nature of the production of the compound nucleus.

A nuclear reaction

Nuclear reaction

In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle from outside the atom, collide to produce products different from the initial particles...

should be described by a complete study of the exit channel (1n,2n,3n etc) excitation functions in order to allow a determination of the optimum energy to be used to maximize the yield.