Investigation of the reaction mechanism for the four-particle photodisintegration of a carbon nucleus

• Published in: Physics of atomic nuclei Vol. 70; no. 5; pp. 839 - 847
• Main Authors: Afanas’ev, S. N., Gorbenko, E. S., Khodyachikh, A. F.
• Format: Journal Article
• Language: English
• Published: United States 01.05.2007
• Subjects: ANGULAR DISTRIBUTION; ASYMMETRY COEFFICIENTS; BERYLLIUM 7; BERYLLIUM 8; BORON 11; BRANCHING RATIO; CARBON; CARBON 11; CARBON 12; DIFFUSION CHAMBERS; ENERGY DEPENDENCE; EXCITATION; EXCITED STATES; LITHIUM 7; MEV RANGE 10-100; NUCLEAR DECAY; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEONS; PHOTONS; PHOTONUCLEAR REACTIONS; REACTION KINETICS
• ISSN: 1063-7788; 1562-692X
• DOI: 10.1134/S1063778807050055

The four-particle photodisintegration of a carbon nucleus in the reactions {sup 12}C({gamma}, p){sup 3}H2{alpha} and {sup 12}C({gamma}, n){sup 3}H2{alpha} is investigated by a method that employs a diffusion chamber in a magnetic field. It is shown that these reactions proceed according a sequential-type scheme: excited states of {sup 11}B and {sup 11}C nuclei decay to weakly excited states of {sup 8}Be, {sup 7}Li, and {sup 7}Be nuclei. It is concluded that nucleons are knocked out from the s shell. In the excitation curve for the 2{alpha} system in the reaction {sup 12}C({gamma}, p){sup 3}H2{alpha}, a resonance is found between the maxima corresponding to the ground and the first excited state of the {sup 8}Be nucleus, and this resonance is identified as a ghost anomaly. The branching fractions of the decay modes are determined. The angular distributions of nucleons in the reaction c.m. frame are measured. The energy dependence of the asymmetry coefficient for the angular distributions is obtained. A fast increase in this coefficient is observed in the energy range 38-40 MeV. It is concluded that the asymmetry coefficient depends on the excitation energy of the final nucleus in the region of intermediate photon energies.