High precision mass measurement of sulfur near N = 28

High-precision mass measurements have been performed on the neutron-rich sulfur isotopes 40-44S using the Low Energy Beam and Ion Trap (LEBIT) 9.4 T Penning trap at the NSCL. Produced via projectile fragmentation with a 48Ca primary beam, the ions were converted into a low-energy beam via gas stopping and then transferred into a 9.4 T Penning trap mass spectrometer. Mass uncertainties as low as 20 keV have been achieved in a mass region with important nuclear structure effects like the disappearance of the N=28 shell closure and the appearance of a strong subshell closure in neighboring Z=14. The experiments were of further technical interest because of the type of beams that can be extracted from gas stoppers. Not only atomic sulfur ions but also several different radio-molecules were used for the mass determination.