High-energy two-neutron removal fromBe10

Abstract

A kinetically complete measurement of the $^{12}\mathrm{C}$($^{10}\mathrm{Be}$, $\ensuremath{\alpha}+\ensuremath{\alpha}+n$) and ($^{10}\mathrm{Be}$, $\ensuremath{\alpha}+\ensuremath{\alpha}$) reactions has been performed at a beam energy of 30 MeV/nucleon. The charged beam velocity particles were detected in an array of Si-CsI detectors placed at zero degrees, and the neutrons in an 81-element neutron array. The coincident detection of the final-state particles, produced in the breakup of $^{10}\mathrm{Be}$, allowed the reconstruction of the excitation energy in the $^{8}\mathrm{Be}$ and $^{9}\mathrm{Be}$ systems. States in $^{8}\mathrm{Be}$ were identified, in particular the ground and first-excited states; and in $^{9}\mathrm{Be}$, states at 1.68, 2.43, and (2.78, 3.05) MeV were observed. The population of these levels, in particular the 2.43 MeV $5/{2}^{\ensuremath{-}}$ level, suggests that collective excitations play an important role in the neutron removal process. Distorted wave Born approximation and Glauber-type calculations have been used to model the direct neutron removal from the $^{10}\mathrm{Be}$ ground state and the two-step removal via inelastic excitations of the $^{10}\mathrm{Be}$(2${}^{+}$) and $^{9}\mathrm{Be}(5/{2}^{\ensuremath{-}})$ excited states.