The basic unknowns in the CC theory are the cluster amplitudes , of one, two, three electron excited determinants etc. Using (10) and (11), the exponential operator () acting on  may be written as

The first term () in the above expression generates the HF function () while all the singly excited (w.r.t. ) configurations are produced by the action of  on . The group of terms generated by  include all connected double excitations () and also all disconnected double excitation (). Similarly, the group of terms generated by  represent all triply excited states which include the conventional or direct triples () or product triples ( or ) and, so on for quadruply excited configurations. Following the CC recipe, the Schrodinger equation for the stationary states of H can be written in the form