Precision Mass Measurements of Neutron-Rich Scandium Isotopes Refine the Evolution of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>32</mml:mn></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>34</mml:mn></mml:math> Shell Closures

We report high-precision mass measurements of $^{50-55}$Sc isotopes performed at the LEBIT facility NSCL and TITAN TRIUMF. Our results provide a substantial reduction their uncertainties indicate significant deviations, up to 0.7 MeV, from previously recommended values for $^{53-55}$Sc. The this work an important update description emerging closed-shell phenomena neutron numbers $N=32$ $N=34$ above proton-magic $Z=20$. In particular, they finally enable complete precise characterization trends in ground state binding energies along isotone, confirming that empirical shell gap peak doubly-magic $^{52}$Ca. Moreover, our data, combined with other recent measurements, does not support existence closed $^{55}$Sc $N=34$. were compared predictions both \emph{ab initio} phenomenological nuclear theories, which all had success describing but highly disparate isotone.