Low-lying intruder 1− state in 12Be and the melting of the N=8 shell closure

A new experimental study of the12Be cluster structure

“…The secondary beam of 12 Be at 29MeV/u was tracked onto a 100mg/cm 2 carbon target by two PPACs with a position resolution(FWHM) of about 1mm. The fragmentation products were recorded by a downstream zero-degree telescope consisting of a 300µm-thick double-sided silicon strip detector(DSSD) a e-mail: yeyl@pku.edu.cn and a 4*4 CsI scintillator array.…”

“…However, most of these resonances were not observed in a later experiment by Charity et al with significantly better statistics [16]. This brings in severe disputation on the description of molecular states in 12 Be. So, more measurements are necessary to check the existence of these MR states and related α-4n-α cluster structure in 12 Be.…”

“…The N=8 shell closure was found quenching in 12 Be [9][10][11][12], which may be related to the α-clustering [13,14]. One possible method to probe the Molecular-Resonance(MR) states is to apply the inelastic excitation followed by coincidently recording the decay products [15,16,19].…”

“…So, more measurements are necessary to check the existence of these MR states and related α-4n-α cluster structure in 12 Be. Here we present experimental data for the breakup of 12 Be into 2 helium fragments via inelastic scattering off carbon target at 29MeV/u.…”

Study of 14Be with core excitation

“…Fortune et al [14] reported five low-lying states of 12 Be with E x = 0.0(0 + ), 2.1(2 + ), 2.7(0 + ), 4.6(2 + ) and 5.7(4 + ) MeV, where the spin assignments of the last three states are only tentative. In recent years much evidence has been accumulated that 12 Be does not have a good N = 8 neutron closed shell [15][16][17]. Iwasaki et al [15] observed a strong excitation of the 12 Be 2 + 1 state in inelastic proton scattering from 12 Be, consistent with a strong quadrupole deformation.…”