Experiments on the transmutation of sodium by deuterons

The transmutations of sodium under bombardment with high speed particles have previously been studied in considerably less detail than have those of elements of lower atomic number. In an early paper Lawrence (1934) reported that the bombardment of sodium with deuterons led to the formation of a radioactive body of half life 15 hr. By chemical means it was shown that this body was an isotope of sodium and its formation was attributed to the process 23Na + 2H→24Na + 1H. (1) The energy distribution of the protons emitted in this reaction was also investigated by Lawrence (1935). He found that bombardment of sodium targets with deuterons of energy 2.15 x 106 eV led to the emission of two groups of protons with ranges 49 ± 2 cm. and 17 ± 1 cm. respectively. The emission of a group of alpha-particles of range 6.5 ± 0.3 cm. was also reported and was attributed to the following transmutation: 23Na + 2H→21Ne + 4He. (2) From these observations the masses of both 24Na and 23Na were calculated and found to be 24.000 ± 0.003 and 22.992 ± 0.001 respectively. The above investigation was admittedly only preliminary. In the absence of accurate mass spectrographic measurements of the masses of any of the atoms lying between 22Ne and 28Si in the periodic table it is important that the energy release in each of the reactions (1) and (2) be known accurately in order to establish reliable values for the nuclear masses in this region. The work described here forms a more detailed investigation of the above reactions and the atomic masses deduced from our observations are believed to be accurate to within 0.0003 mass unit. The distribution in range of both the alpha-particle and proton emission has been found to be much more complicated than was previously supposed and from measurements of the ranges of the various groups of particles the energies of several levels of excitation of the nuclei 21Ne and 24Na have been determined.