Thomas Bonner

THE DISINTEGRATION OF NITROGEN BY FAST NEUTRONS

Abstract The disintegration of nitrogen by fast neutrons has been studied using a grid-type ionization chamber filled with nitrogen or a nitrogen-argon mixture. Monoenergetic neutrons for studying the reactions from a neutron energy of 1.3 to 8.2 MeV were produced by the T 3 (p, n)He 3 and D(d, n)He 3 reactions. One group of protons, three alpha particle groups, and a group of tritons were observed as disintegration products of the neutron reactions in nitrogen. The N 14 (n, p)C 14 reaction leaving C 14 in its ground state was studied from 1.3 to 4.3 MeV and the maximum cross section observed was 230 mb. Four groups of α-particles leading to the ground, 2.14, 4.46, and 5.03 MeV levels in B 11 were observed in the experiment. The cross section for the α-particle group leading to the ground state of B 11 varied from 5 mb at a neutron energy of 1.3 MeV to 390 mb at 4.2 MeV and decreased for higher neutron energies. Triton emission leading to the ground state of C 12 was observed above a neutron energy of 5.6 MeV. Above 7 MeV, the cross sections for disintegration by emission of each of the alpha groups and by triton emission were about equal and were approximately 40 mb. The cross sections show many narrow resonances in the neutron energy range studied. The data show that alpha emission relative to proton and neutron emission from these highly excited states of N 15 is much more probable than expected on shell model considerations.

Disintegration of O16 and C12 by fast neutrons

Abstract The disintegration of O 16 and C 12 by fast neutrons has been studied using a grid-type ionization chamber filled with CO 2 Ar or CO 2 Kr mixtures. Mono-energetic neutrons for studying the reactions from 5.0–8.8 MeV were produced with the D(d, n)He 3 reaction using a gas target. The α-particle group from the O 16 (n, α)C 13 reaction leaving C 13 in its ground state was studied over the entire energy range. The excitation function showed 21 resonances corresponding to excited states in O 17 . The cross section varied from 2–206 mb. The α-particle group leaving C 13 in its first excited state was studied from 7.6–8.7 MeV, the cross section increasing from about 3–12 mb. Unresolved α-particle groups leaving C 13 in its second and third excited states were studied from 8.1–8.7 MeV, the cross section decreasing from an estimated 30–8 mb. The α-particle group from the C 12 (n,α)Be 9 reaction leaving Be 9 in its ground state was studied from 7.9–8.7 MeV. The cross section increased from 60–76 mb at 8.0 MeV and then decreased to 32 mb at 8.7 MeV.

Gamma radiation from excited states of F18, Na22 and Ne22

Abstract Gamma radiation from the proton bombardment of O18, the He3 bombardment of O16, and the alpha bombardment of F19 have been studied by means of a magnetic lens photo conversion spectrometer and a NaI spectrometer. Gamma rays from the bombardment of an O18 target with protons were observed with energies 0.511 ± 0.004, 0.666 ± 0.005, 0.938 ± 0.006, 1.043 ± 0.008, 1.082 ± 0.010 and 1.990 ± 0.010 MeV. Gamma rays from the bombardment of an O16 target with 2.83 MeV He3 particles were observed with energies of 0.189 ± 0.005, 0.66 ± 0.02, 0.95 ± 0.02, 1.07 ± 0.02, 1.71 ± 0.03, 2.14 ± 0.03, 2.54 ± 0.03, and 3.11 ± 0.05 MeV. The internal conversion coefficient of the 0.189 MeV radiation was measured to be (2.86 ± 0.4) × 10−3. The energies of the gamma radiation from the alpha particle bombardment of a F19 target were observed to be 0.073 ± 0.002, 0.109 ± 0.002, 0.586 ± 0.004, 0.892 ± 0.005, 1.275 ± 0.008, 1.530 ± 0.010 and 2.090 ± 0.016 MeV. The internal conversion coefficients of the 0.073, 0.109 and 0.586 MeV gammas were observed to be (4.5 ± 0.4) × 10−3, (2.8 ± 0.5) × 10−3and (1.14 ± 0.3) × 10−4, respectively.