Analysis of primary electric dipole gamma rays from slow-neutron capture by Ca isotopes

Journal Article · Sat Aug 01 04:00:00 EDT 1987 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.36.533· OSTI ID:5943889

Kahane, S; Lynn, J E; Raman, S

We have analyzed the available data on the primary E1 transitions in the thermal-neutron capture by even isotopes of calcium with the aim of determining the relative importance of direct and compound-nucleus mechanisms of capture in these nuclides. In some of these cases, the thermal-neutron scattering length, as well as the spectroscopic factors of the final states, is known, and an absolute estimate of the direct capture cross sections can be made. In these cases (/sup 40/Ca, /sup 44/Ca) the estimates made from a specialized optical model (which reproduces the scattering length precisely) and a global optical model with a valency contribution from a local level are in agreement and are also generally close in absolute value to the experimental cross sections. The detailed deviations can be accounted for as a compound-nucleus contribution to the transitions, which fluctuates, but has an overall magnitude in agreement with Cameron's semiempirical relationship for this mechanism. In both nuclides the compound-nucleus contribution to the capture can plausibly be attributed to a bound local level. For /sup 48/Ca there is some indirect evidence for the value of the thermal-neutron scattering length, and the use of this value in the calculations of direct capture leads to agreement with the data. There is no evidence for an important compound-nucleus contribution in this magic number nucleus. In /sup 42/Ca and /sup 46/Ca the thermal-neutron scattering length can be adjusted to ''best fit'' the calculation of direct capture from the optical model to the experimental data. After this adjustment the detailed agreement between theory and data is very good, indicating the major predominance of the direct mechanism in capture at thermal-neutron energies by these nuclides.

• Research Organization: Nuclear Research Centre, Negev, Beer-Sheva, Israel 84190
• OSTI ID: 5943889
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 36:2; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

651520* -- Nuclear Properties & Reactions
A=39-58
Experimental
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALKALINE EARTH ISOTOPES
BARYON REACTIONS
CALCIUM 40 TARGET
CALCIUM 42 TARGET
CALCIUM 44 TARGET
CALCIUM 46 TARGET
CALCIUM 48 TARGET
CALCIUM ISOTOPES
CAPTURE
COMPOUND-NUCLEUS REACTIONS
CROSS SECTIONS
DIMENSIONS
DIPOLE MOMENTS
E1-TRANSITIONS
ELECTRIC DIPOLE MOMENTS
ELECTRIC MOMENTS
ELECTROMAGNETIC RADIATION
ENERGY-LEVEL TRANSITIONS
GAMMA RADIATION
HADRON REACTIONS
IONIZING RADIATIONS
ISOTOPES
LENGTH
MULTIPOLE TRANSITIONS
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
OPTICAL MODELS
RADIATIONS
SCATTERING LENGTHS
SPECTROSCOPIC FACTORS
TARGETS