Application of the Trojan Horse Method to study neutron induced reactions: the ¹⁷O(n,α)¹⁴C reaction

The reaction ¹⁷O(n,α)¹⁴C was studied using virtual neutrons coming from the quasi-free deuteron break-up in the three body reaction ¹⁷O+d → α + ¹⁴C + p. This technique, called virtual neutron method, extends the Trojan Horse method (THM) to neutron-induced reactions allowing to study the reaction cross section avoiding the suppression effects coming from the penetrability of the centrifugal barrier. For incident neutron energies from thermal up to a few hundred keV, direct experiments have shown the population of two out of three expected excited states at energies 8213 keV and 8282 keV and the influence of the sub-threshold level at 8038 keV. In the present experiment the ¹⁸O excited state at E* = 8.125 MeV, missing in the direct measurement, is observed. The angular distributions of the populated resonances have been measured for the first time. The results unambiguously indicate the ability of THM to overcome the centrifugal barrier suppression effect and to pick out the contribution of the bare nuclear interaction. (authors)