The beta-decay of ${\mathrm{F}}^{10}$ has been investigated with a lens spectrometer using sources activated by the ${\mathrm{F}}^{19}\mathrm{}(d,p)\mathrm{}{\mathrm{F}}^{20}$ reaction. A simple beta-ray spectrum of allowed shape is observed having an end-point energy of 5.406±0.017 Mev. Beta-emission is followed by a 1.631±0.006 Mev gamma-ray from an excited state of ${\mathrm{Ne}}^{20}$. The gamma-ray energy was checked by comparing with the ${\mathrm{Sb}}^{124}$ gamma-ray, measured as 1.692±0.005 Mev, and by failure to observe photoneutrons from Be. Beta-ray branching to the ground state of ${\mathrm{Ne}}^{20}$, if present, has a relative intensity of less than 1 percent. The total ${\mathrm{F}}^{20}$ disintegration energy, 7.038±0.018 Mev, is used together with other nuclear data to derive a ${\mathrm{Ne}}^{20}$ mass which is independent of mass spectrographic measurements. The result, ${\mathrm{Ne}}^{20}$=19.998794±0.000026 amu, is in agreement with mass spectrographic values.

• Received 25 July 1952

DOI:https://doi.org/10.1103/PhysRev.88.1257