Neutron occupancy of 0d5/2 orbital in 24O

The partial one-neutron removal cross section of 24 O leading to the first ex- cited state in 23 O has been measured to be 65.7 5.3 mb with a proton target in inverse kinematics at the beam energy of 62 MeV/nucleon. The decay energy spectrum of the neutron unbound state of 23 O was reconstructed from the measured four momenta of 22 O and the emitted neutron. A sharp peak was observed at Edecay = 48 3 keV, confirming the previous measurements. The measured partial longitudinal momentum distribution of 23 O showed the d-wave knockout character, providing a support for the J assignment of 5/2 + for this state. The spectroscopic factor for the neutrons in 0d5=2 orbital was deduced, for the first time, to be C 2 S (0d5=2) = 3.7 0.3 (preliminary) by comparing with the result of Glauber model. The relatively large spectroscopic factor supports the N = 16 shell closure in the neutron drip-line nucleus 24 O.