Measurements of Light Masses with the Mass Synchrometer

A complete account is presented of all results obtained with the mass synchrometer before November, 1957. Included, besides measurements made before March, 1957, tentative values of most of which have been published with little discussion by the author and/or by others, is an extensive later set of measurements on 40 parent ion doublets. From least squares analyses of 39 of these doublet values and of 11 selected earlier values and from three other earlier values are derived what are believed to be the best values obtainable from all synchrometer data of the mass excesses of the 14 nuclides from which all ions studied are composed. These are ${\mathrm{H}}^1$, ${\mathrm{D}}^2$, ${\mathrm{He}}^4$, ${\mathrm{B}}^{10}$, ${\mathrm{B}}^{11}$, ${\mathrm{C}}^{12}$, ${\mathrm{N}}^{14}$, ${\mathrm{O}}^{18}$, ${\mathrm{Ne}}^{20}$, ${\mathrm{Ne}}^{22}$, ${\mathrm{S}}^{32}$, ${\mathrm{Cl}}^{35}$, ${\mathrm{Cl}}^{37}$, and ${\mathrm{A}}^{40}$. Best values of all measured doublets are also tabulated. Statistical analyses indicate that, for external consistency of results, the internal errors given should be multiplied by either 2.35 or 3.6 (the larger fraction applying primarily in cases where ions are formed by molecular dissociation). They also indicate that, except in cases where ions are formed with appreciable kinetic energies, the external error of the mean of twenty measurements of a doublet separation made with present techniques is about one part in 4×${10}^7$ of the mass number. The agreement of the best values with the latest comparable values obtained at the University of Minnesota is excellent for the important mass excess C-12 and satisfactory in nearly all other cases. Agreement with comparable values obtained from measurements of nuclear reaction energies is fairly good except for ${\mathrm{C}}_3$-H${\mathrm{Cl}}^{35}$ and ${\mathrm{Cl}}^{35}$-35, the synchrometer values of which appear to be in error.