The Transmutation of Fluorine by Proton Bombardment and the Mass of Fluorine 19

Fluorine has been transmuted by bombardment with protons into oxygen and helium. The number of transmutations has been followed from a proton energy of 0.675 to 1.63×${10}^6$ electron-volts. The alpha-particles emitted have a range greater than 6 cm. Their range increases with proton energy in the expected manner. The short range alpha-particles observed both by us and by other workers are probably due to a boron contamination. Professor Oppenheimer has calculated, along the lines of the Gamow theory, the manner in which the probability of transmutation should vary with the energy of the protons. The measurements are in excellent agreement with the theory. The mass of the fluorine atom that is calculated from the reaction, 19.0031, is in excellent agreement with other transmutation data, but not with the value usually accepted, namely 19.000.