Neutron occupancy of 0d5/2 orbital in 24O

The partial one-neutron removal cross section of O-24 leading to the first excited state in O-23 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 O-23 was reconstructed from the measured four momenta of O-22 and the emitted neutron. A sharp peak was observed at E-decay = 48 +/- 3 keV, confirming the previous measurements. The measured partial longitudinal momentum distribution of O-23* showed the d-wave knockout character, providing a support for the J(pi) assignment of 5/2(+) for this state. The spectroscopic factor for the neutrons in 0d(5/2) orbital was deduced, for the first time, to be (CS)-S-2 (0d(5/2)) = 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 O-24.