The excitation function of gamma-rays produced by the proton bombardment of fluorine has been extended from 2.1 to 5.4 Mev with a resolution of 0.1 percent. 17 new resonances were observed with maxima at 2.32, 2.51, 2.63, 2.80, 3.02, 3.19, 3.49, 3.92, 4.00, 4.29, 4.49, 4.57, 4.71, 4.78, 4.99, 5.07, and 5.20 Mev. The ${\mathrm{Fe}}^{19}\mathrm{}(p,n)\mathrm{}{\mathrm{Ne}}^{19}$ threshold was determined to be 4.253±0.005 Mev, and the neutron yield in the forward direction was extended to 5.3 Mev. Maxima occur at 4.29, 4.46, 4.49, 4.57, 4.62, 4.71, 4.78, 4.99, 5.07, and 5.20 Mev. The ${\mathrm{Ne}}^{19}$-${\mathrm{F}}^{19}$ mass difference was calculated from the threshold measurement to be ${0.00349}_9$ amu.

• Received 21 November 1951

DOI:https://doi.org/10.1103/PhysRev.85.849