Determination of 1 p - and 2 p -stripping excitation functions for ^16 O+ ^142 Ce 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 2 p -stripping cross sections at θ _c.m.=180^∘ have been determined for the system ^16 O+ ^142 Ce 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 ^142Ce(^16O,^15N)^143Pr and ^142Ce(^16O,^14C)^144Nd 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 1 p -stripping. For 2 p -stripping, cluster transfer of two protons has been found to have dominant contribution. Measured transfer probabilities for 1 p - and 2 p -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.