Total reaction and neutron-removal cross sections of (30-60)A MeV He and Li isotopes on Pb

Abstract

Total reaction cross sections sigma(R) of (30-60)A MeV He-4,He-6,He-8 and Li-6,Li-7,Li-8,Li-9,Li-11 on Ph, and 2n-removal cross sections sigma-(2n) of He-6,He-8 and Li-11 on Pb, were measured by injecting magnetically separated, focused, monoenergetic, secondary beams of those projectiles into a telescope containing Pb targets separated by thin Si detectors. All these sigma(R)s (except He-4), and sigma-(2n) for He-6 and Li-11, are underpredicted by microscopic model calculations which include only nuclear forces. Better agreement is achieved by including electromagnetic dissociation in the model, for those projectiles for which either the electric dipole response functions or the dominant photodissociation cross sections were known. The cross sections sigma-(4n) for He-8, sigma-(xn) for Li-7,Li-8,Li-9, and (sigma-(3n)+ sigma-(4n)) for Li-11 were found to be less than or equal to 0.7 b. All sigma(R)s were measured to better than 5% accuracy, showing that the method is usable for other target elements sandwiched into a Si telescope.