A chemical process in which the @R05182@ has a @L03515@ that is longer than its period of rotation is called an indirect reaction (in contrast to a @D01773@). In a @M03982@ 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 @C01206@. (They are sometimes called complex reactions, but this usage is not recommended in view of the danger of confusion with @CT07545@ reactions, which occur in more than one step).