Large longitudinal spin alignment generated in inelastic nuclear reactions

Abstract

Large longitudinal spin alignment of E/A=24 MeV 7 Li projectiles inelastically excited by Be, C, and Al targets was observed when the latter remain in their ground state. This alignment is a consequence of an angular-momentum-excitation-energy mismatch which is well described by a DWBA cluster-model (α + t). The longitudinal alignment of several other systems is also well described by DWBA calculations, including one where a cluster model is inappropriate, demonstrating that the alignment mechanism is a more general phenomenon. Predictions are made for inelastic excitation of 12 C for beam energies above and below the mismatch threshold.

Single-nucleon knockout cross sections for reactions producing resonance states at or beyond the drip line

“…The widths of the observed E * T arget peaks are consistent with the simulated resolution for this quantity. Similar-shaped E * T arget distributions were observed for inelastic scattering of 7 Be (E/A=65.5 MeV) and 6 Li (E/A=36.6 MeV) projectiles on 9 Be targets [24] and for 7 Li projectiles on 9 Be, 12 C, and 27 Al targets at E/A=24 MeV [25,26]. The E * T arget =0 component has a more forward focused angular distribution than that of the tail component.…”

Using spin alignment of inelastically-excited fast beams to make spin assignments: the spectroscopy of 13O as a test case

“…The spin of the target nucleus was shown to be unimportant in Ref. [3] where similar spin alignments for 7 Li excited state was observed with both a J=3/2 9 Be and a spin-zero 12 C target.…”

“…Previous studies of inelastic scattering with fast beams have shown the possibility of achieving strong spin alignment if the target nucleus remains in its ground state after the inelastic scattering [1][2][3][4]. Figure 3 shows the distributions of target excitation energy deduced from the center of mass of the p+ 12 N and 2p+ 11 C events assuming two-body kinematics for inelastic scattering reactions.…”

“…Further re-strictions to their spins can be obtained from knowledge of their spin alignment in the reactions. In the excitation of 7 Li and 7 Be projectiles from their 3/2 − ground state to the 7/2 − excited state, large spin alignments were found when the target nucleus remained in its ground state and it was argued that this was largely independent of the excitation mechanism but was based on general arguments [2,3]. In this work, we assume the proton decays from the observed levels can only be s, p, and d-wave in nature giving us a maximum possible spin of 9/2 + for decay to the excited states of 12 4.…”

“…This spin alignment was observed only when the target nucleus remained in its ground state after the reactions. Hoff et al showed this alignment was due to a matching condition in grazing collisions and not dependent on the excitation mechanism but could be understood from general principles [2,3]. * Present Address: Lawrence Livermore National Laboratory, Livermore, CA 94550 † Present Address: Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433, USA ‡ Present Address: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA For an excited state with the same parity as the beam, Hoff et al showed that this matching condition largely restricts collisions to those where the magnitude of the orbital angular momentum was unchanged.…”