One-neutron knockout reaction of 17C on a hydrogen target at 70 MeV/nucleon

First experimental evidence of the population of the first 2−2− state in 16C above the neutron threshold is obtained by neutron knockout from 17C on a hydrogen target. The invariant mass method combined with in-beam γ  -ray detection is used to locate the state at 5.45(1) MeV. Comparison of its populating cross section and parallel momentum distribution with a Glauber model calculation utilizing the shell-model spectroscopic factor confirms the core-neutron removal nature of this state. Additionally, a previously known unbound state at 6.11 MeV and a new state at 6.28(2) MeV are observed. The position of the first 2−2− state, which belongs to a member of the lowest-lying p–sd cross shell transition, is reasonably well described by the shell-model calculation using the WBT interaction.