Volume and surface symmetry energy coefficients

In this paper we study the volume and surface symmetry energy coefficients (csym(V) and csym(S)) by using the double differences of ``experimental'' symmetry energies. We assume asym=csym(V)-csym(S)/A1/3 and obtain csym(V)=31.26±0.32 MeV and csym(S)=52.15±1.12 MeV, or csym(V)=32.10±0.31 MeV and csym(S)=58.91±1.08 MeV, depending on the form of the Wigner energy. The uncertainties of these coefficients are smaller than those in the literature. The values of csym(V) and κS/V are unstable for different mass regions if one assumes asym=csym(V)/(1+κS/V/A1/3). We notice an odd-even staggering in the double differences of ``experimental'' symmetry energies under a few situations, and suggest that the pairing interaction might not be properly taken into account in the current mass formulas.