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Publisher Summary This chapter explores a few nucleon reactions for mass fields greater than three. The majority of these experiments are being done to investigate quasi-free (QF) processes with all possible pairs being observed, including both QF scattering and QF reactions. An important question being addressed is to what extent distorted waves improve the impulse approximation predictions. In few cases, substantial improvements are obtained using distorted waves, but in the tightly bound alpha particle, evidence that plain waves are as appropriate as distorted waves exists. An experimental situation that can cause problems is the spectral structure as a result of 4He excited states. This can cause severe problems with n–n scattering-length experiments, and the success or failure of these experiments can depend upon preselecting the most advantageous regions of phase space. Also, Coulomb FSI occurs in few of these experiments, and this FSI can produce dramatic reductions in the observed cross sections. This effect occurs when two charged particles have almost zero relative energy and no threshold resonance structure. The Coulomb repulsion can dominate, causing a striking dip in the cross section and can interfere with the investigation of other processes. |