Analysis of low-energy direct reactions and the novel one-step cross section Original Research Article

Inclusive non-elastic nucleon emission is usually described as a one-step direct reaction followed by gradual absorption of the remaining flux into the quasibound particle-hole states of the multistep compound reaction chain. We present a sum rule analysis of the cross sections calculated in the framework of the quantal theory of Feshbach, Kerman and Koonin which shows that the experimental data cannot be explained by one-step direct reactions only. The closed-form one-step reaction cross section is expressed as a sum of contributions due to incoherent excitation of particle-hole pairs of orbital angular momentum transfer l > 4 and coherent excitation of collective vibrations of multipolarity not exceeding λ = 4. The calculation of multistep cross sections with the non-normal DWBA matrix elements is discussed.