Thermal-neutron capture by silicon isotopes

• Published in: Physical review. C, Nuclear physics Nuclear physics, 1992-09, Vol.46 (3), p.972-983
• Main Authors: Raman, S, Jurney, ET, Starner, JW, Lynn, JE
• Format: Article
• Language: English
• Subjects: 663220 - Electromagnetic Transitions- (1992-); 663430 - Nucleon-Induced Reactions & Scattering- (1992-); 663530 - Nuclear Mass Ranges- A=20-38- (1992-); BARYON REACTIONS; BARYONS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; CAPTURE; CROSS SECTIONS; DATA; E1-TRANSITIONS; ELEMENTARY PARTICLES; ENERGY LEVELS; ENERGY-LEVEL TRANSITIONS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; EXCITED STATES; EXPERIMENTAL DATA; FERMIONS; GAMMA SPECTRA; HADRON REACTIONS; HADRONS; HOURS LIVING RADIOISOTOPES; INFORMATION; ISOTOPES; LIGHT NUCLEI; MULTIPOLE TRANSITIONS; NEUTRON REACTIONS; NEUTRONS; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR REACTIONS; NUCLEI; NUCLEON REACTIONS; NUCLEONS; NUMERICAL DATA; RADIOISOTOPES; SILICON 28 TARGET; SILICON 29; SILICON 29 TARGET; SILICON 30; SILICON 30 TARGET; SILICON 31; SILICON ISOTOPES; SPECTRA; STABLE ISOTOPES; TARGETS; THERMAL NEUTRONS
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PhysRevC.46.972

We have studied primary and secondary {gamma} rays (46 in {sup 29}Si, 107 in {sup 30}Si, and 33 in {sup 31}Si) following thermal-neutron capture by the stable {sup 28}Si, {sup 29}Si, and {sup 30}Si isotopes. Almost all of these {gamma} rays have been incorporated into corresponding level schemes consisting of 12 excited levels in {sup 29}Si, 28 in {sup 30}Si, and 9 in {sup 31}Si. In each case, the observed {gamma} rays account for nearly 100% of all captures. The measured neutron separation energies for {sup 29}Si, {sup 30}Si, and {sup 31}Si are 8473.56{plus minus}0.04, 10609.24{plus minus}0.05, and 6587.40{plus minus}0.05 keV, respectively. The measured thermal-neutron capture cross sections for {sup 28}Si, {sup 29}Si, and {sup 30}Si are 169{plus minus}4, 119{plus minus}3, and 107{plus minus}3 mb, respectively. In all three cases, primary electric-dipole ({ital E}1) transitions account for the bulk of the total capture cross section. We have calculated these {ital E}1 partial cross sections using direct-capture theory. The agreement between theory and experiment is satisfactory.