Study of the N = 28 shell closure in the Ar isotopic chain.

The structure of the neutron-rich nucleus ⁴⁷Ar has been investigated through the d( ⁴⁶Ar, ⁴⁷Ar)p transfer reaction. The radioactive beam of ⁴⁶Ar at 10 A·MeV was provided by the SPIRAL facility at GANIL. The protons corresponding to a neutron pick-up on bound or unbound states mechanism in ⁴⁷Ar nuclei were detected at backward angles by the position-sensitive Si array-detector MUST. The transfer-like ejectiles were detected in the SPEG spectrometer. Level scheme, spin assignments and spectroscopic factors have been deduced for ⁴⁷Ar and compared to shell model predictions. They suggest a slight erosion of the N = 28 shell gap from the weakening of the spin-orbit interaction arising from the f and p orbitals. These spectroscopic information are subsequently used to infer ( n,γ) reaction rates in the Ar isotopic chain to understand the origin of the ⁴⁸Ca/ ⁴⁶Ca abnormal isotopic ratio observed in certain inclusions of meteorites. [ABSTRACT FROM AUTHOR]