A chemical process in which the reactive complex has a lifetime that is longer than its period of rotation is called an indirect reaction (in contrast to a direct reaction). In a molecular-beam experiment the products of such reactions are scattered at random with reference to the centre of mass of the system. Indirect reactions are also called complex-mode reactions. (They are sometimes called complex reactions, but this usage is not recommended in view of the danger of confusion with composite reactions, which occur in more than one step).