Fay Ajzenberg’s research while affiliated with Boston University and other places

DOI:https://doi.org/10.1103/RevModPhys.27.77

The B10(p, n)C10 reaction has been investigated at 30, 60, 90, 120, and 150 degrees in the laboratory system by the method of proton recoils in thick photographic emulsions. The mean energy of the incident protons was 17.2+/-0.15 Mev. The results indicate a ground-state Q value of -4.35+/-0.2 Mev, yielding a mass defect of 18.6 Mev for C10 in good agreement with beta decay results. The data also indicate a level in C10 at 3.34+/-0.2 Mev and partly resolved levels at excitation energies >~5 Mev. The angular distributions of the neutrons to the ground state and to the 3.34-Mev state are shown.

The N14(p, n)O14 reaction has been investigated at 30, 60, and 150 degrees in the laboratory system by the method of proton recoils in thick nuclear emulsions. The energy of the incident protons was 17.3+/-0.1 Mev, and the thickness of the melamine target was 0.2 Mev. The results indicate a ground-state Q value of -6.03+/-0.2 Mev, yielding a mass defect for O14 of 12.2 Mev, in good agreement with beta-decay results. The data also indicate levels in O14 at excitation energies greater than 5.5 Mev.

Be9 has been bombarded with 6.59-Mev protons. The resultant neutrons, studied by means of nuclear emulsions, indicate an excited state of B9 at 2.37+/-0.04 Mev. A continuum of neutrons has also been observed.

DOI:https://doi.org/10.1103/RevModPhys.24.321

Previous measurements on the Be9(d,n)B10 neutron spectrum at 0° and 80° have been extended to 10°, 30°, and 45° to check the energy level assignments and to deduce the parity of the levels from a Butler analysis of the angular distributions. The observed neutron groups correspond to levels of B10 at 0.72, 1.75, 2.15, 3.53, 4.78, 5.14 (doublet), 5.37 (?), 5.58, 5.72 (?), 5.93, 6.12 (possibly doublet), 6.38, 6.58, and 6.77 Mev. The estimated uncertainty is 0.06 Mev for the first five states of B10 and 0.04 Mev for the higher energy levels. The Butler analysis of the angular distribution data indicates that the ground state and the first four excited states of B10 are of even parity and that both components of the 5.14-Mev doublet are probably odd parity states. Parity assignments for some of the other energy levels have been attempted. The spins of these states cannot be uniquely determined on the basis of the Butler analysis, but the possible spin limits are listed. A Be9(d,p)Be10 exposure was also made. There do not appear to be any states in Be10 between the ground state and the known 3.37-Mev level.

The ranges of protons recoiling from monoergic neutrons have been used to determine a range-energy relation for Eastman NTA emulsions. The experimental results for proton energies from 1 to 17 Mev agree closely with Webb's computed range-energy relation.

DOI:https://doi.org/10.1103/PhysRev.83.693

The neutron spectrum at 0° and at 80° from the Be9(d,n)B10 reaction has been investigated by means of nuclear emulsions. Energy levels of B10 at 0.77, 1.79, 2.22, 3.59, 4.79, 5.12, 5.91, 6.11, 6.57, and 6.81 Mev have been observed as have possible levels at 5.58, 5.68, and 6.38 Mev. There is evidence for multiplicities at 5.12 and, possibly, at 6.11 Mev. No neutron groups were observed which would correspond to levels at 1.4 and 2.85 Mev. This result is in disagreement with the picture of equally spaced levels in B10. An attempt is made to explain the results that led to this picture.