Atomic Masses in the Region about Mass 40

Abstract

The double-focusing mass spectrometer developed for the precise determination of atomic masses has been improved. A redetermination of the mass doublets 4${\mathrm{C}}^{12}$-${\mathrm{S}}^{32}$${\mathrm{O}}^{16}$, ${2\mathrm{O}}^{16}$-${\mathrm{S}}^{32}$, and ${\mathrm{C}}^{12}$${\mathrm{H}}_{4}$-${\mathrm{O}}^{16}$ lead to the following masses: ${\mathrm{H}}^{1}$ = 1.008146\ifmmode\pm\else\textpm\fi{}3, ${\mathrm{C}}^{12}$ = 12.003842\ifmmode\pm\else\textpm\fi{}4, and ${\mathrm{S}}^{32}$ = 31.982236\ifmmode\pm\else\textpm\fi{}7. The relation of these results to those of other investigators is discussed.Mass doublet comparisons between hydrocarbon fragments and ${\mathrm{S}}^{32}$, ${\mathrm{S}}^{33}$, ${\mathrm{S}}^{34}$, ${\mathrm{Cl}}^{35}$, ${\mathrm{Cl}}^{37}$, ${\mathrm{A}}^{36}$, ${\mathrm{A}}^{38}$, ${\mathrm{K}}^{39}$, ${\mathrm{K}}^{41}$, ${\mathrm{Ca}}^{42}$, ${\mathrm{Ca}}^{43}$, ${\mathrm{Ca}}^{44}$, ${\mathrm{Ca}}^{48}$, and ${\mathrm{Sc}}^{45}$ have been made and mass values for these nuclides tabulated assuming both mass spectroscopic and nuclear reaction determined mass values for ${\mathrm{H}}^{1}$ and ${\mathrm{C}}^{12}$.The packing fraction curve in the mass 40 region follows the general trends predicted by a formula such as that of Bohr and Wheeler, except at masses 40 and 48 where there appear to be marked discrepancies.