Determination of 1 p- and 2p-stripping excitation functions for O-16+Ce-142 using a recoil mass spectrometer

We report the first direct measurement of differential transfer cross sections using a Recoil Mass Spectrometer. Absolute differential 1 p- and 2p-stripping cross sections at theta(c.m.) = 180 degrees have been determined for the system O-16+Ce-142 by detecting the heavier target-like ions at the focal plane of the Heavy Ion Reaction Analyzer. Focal plane spectra have been compared with the results of a semi-microscopic Monte-Carlo simulation to unambiguously identify the transfer channels. The methodology adopted in this work can be applied to measure multi nucleon transfer cross sections using other similar recoil separators. The experimental excitation functions for the reactions Ce-142(O-16,N-15)Pr-143 and Ce-142(O-16,C-14)Nd-144 have been compared with coupled reaction channels calculations. Shell model calculations have been performed to extract spectroscopic information for the target-like nuclei. An excellent matching between measurement and theory has been obtained for 1p-stripping. For 2p-stripping, cluster transfer of two protons has been found to have dominant contribution. Measured transfer probabilities for 1 p- and 2p-stripping channels have been compared with Time-Dependent Hartree-Fock calculations. Proton stripping channels are found to be more favourable compared to neutron pick-up channels. However, the theory overpredicts the measurement hinting at the need for extended approaches with explicit treatment of pairing correlations in the calculations.