N=16 Spherical Shell Closure in 24o.

The unbound excited states of the neutron drip-line isotope 240 have been investigated via the 240(p, p')230 + n reaction in inverse kinematics at a beam energy of 62 MeV/nucleon. The decay energy spectrum of 240* was reconstructed from the momenta of 230 and the neutron. The spin parity of the first excited state, observed at Ex = 4.65 ± 0.14 MeV, was determined to be Jπ = 2+ from the angular distribution of the cross section. Higher-lying states were also observed. The quadrupole transition parameter ß2 of the 2+1 state was deduced, for the first time, to be 0.15 ± 0.04. The relatively high excitation energy and small ß2 value are indicative of the N = 16 shell closure in 240. [ABSTRACT FROM AUTHOR]