A survey of the (3He, 7Be) reaction at 70 MeV

A study of the (3He, 7Be) reaction has been undertaken using a 70 MeV 3He beam. By surveying a wide range of target nuclides, namely 12, 13C, 16O, 24, 26Mg, 40, 42, 44Ca, 58, 60, 62, 64Ni, 90Zr, 120, 124Sn, 144Sm and 206Pb, systematics of the α-clustering phenomenon were investigated. In addition, masses and energy levels of 60Fe and 120Cd were measured. The 7Be particles were detected in a single wire proportional counter backed by a plastic scintillator in the focal plane of an Enge spectrometer to ensure adequate particle identification. Total energy resolution as small as 140 keV full width at half maximum was obtained, although in most cases the target thickness limited the energy resolution to larger values. Differential cross sections as low as 20 nb/sr were measured. The finite range programs LOLA and LOLITA were used to calculate differential cross sections for comparison to data, assuming the reaction to proceed by a direct α-transfer. The spectroscopic factors which were extracted show a marked decrease with increasing atomic mass number, implying a decrease in surface α-clustering for heavier nuclei.