Finite range calculations for the ($\alpha$, $2\alpha$) reactions are performed for the first time to remove huge inconsistencies obtained earlier in conventional zero range analyses. Vagaries of the energy dependent experimental observations up to 200 MeV are understood using the well-established nuclear radii and distorting optical potentials. The results are found to be sensitive to the short distance behavior of the $\alpha \mathrm{\text{−}}\alpha$ interaction, indicating the utility of the knockout reactions as a probe of the knockout vertex at short distances. Our approach paves the way to include finite range effects in atomic and molecular physics as also in neutron multiplication calculations.

• Received 18 May 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.132503