/sup 206/Pb + n resonances for E = 25--600 keV: s-, p-, and d-wave doorway states and M1 ground-state radiative strength in /sup 207/Pb

Journal Article · Wed Aug 01 00:00:00 EDT 1979 · Phys. Rev., C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.20.478· OSTI ID:6245448

Horen, D J; Harvey, J A; Hill, N W

High resolution neutron transmission and differential scattering measurements have been performed on /sup 206/Pb and the results for E = 25--600 keV are presented. Data analyses were performed utilizing multilevel R-matrix codes. Resonance parameters (i.e., E, l, J, and GAMMA/sub n/) were deduced for a large fraction of the 223 resonances observed. In addition to the previously known doorway in the s-wave channel, the p-wave neutron strength function exhibits significant changes near 40 and 145 keV indicative of doorway states in the p/sub 1/2/ and p/sub 3/2/ channels, respectively. These results are in good agreement with those observed in a study of the /sup 207/Pb + n reaction. It is suggested that these doorway states arise from a (d/sub 5/2/, 3/sup -/) particle-core excitation. The d-wave strength function shows indications of a doorway at about E = 425 keV. The latter represents doorway resonances in the d/sub 3/2/ and d/sub 5/2/ channels which probably arise from a recoupling of the particle-core excitation that has been used to explain the s-wave doorway. A cumulative plot of the number of s-wave resonances vs E shows considerable curvature which indicates an increase of about 12% in the level density per 100 keV of excitation. These data were analyzed in terms of a constant temperature model with a nuclear temperature of about 0.9 MeV. The model reproduced the cumulative plot of d-wave resonances reasonably well up to E approx. = 500 keV, but underestimated the number of p-wave resonances. This indicates a parity dependence of the level density formula for this nucleus. Many of the resonances which had previously been thought to contribute to the ground-state M1 radiative strength are in fact formed by s and d waves, and hence, decay by E1 radiation. We deduce a considerably smaller amount of M1 radiation for E/sub x/ = 6738--7340 keV in /sup 207/Pb than had been reported earlier.

• Research Organization: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
• OSTI ID: 6245448
• Journal Information: Phys. Rev., C; (United States), Journal Name: Phys. Rev., C; (United States) Vol. 20:2; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARYON REACTIONS
CAPTURE
CROSS SECTIONS
E1-TRANSITIONS
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL DENSITY
ENERGY-LEVEL TRANSITIONS
EVEN-ODD NUCLEI
HADRON REACTIONS
HEAVY NUCLEI
INELASTIC SCATTERING
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KEV RANGE
KEV RANGE 10-100
KEV RANGE 100-1000
LEAD 206 TARGET
LEAD 207
LEAD ISOTOPES
M1-TRANSITIONS
MATRICES
MULTIPOLE TRANSITIONS
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
PARTIAL WAVES
R MATRIX
RADIOISOTOPES
RESONANCE SCATTERING
S WAVES
SCATTERING
SECONDS LIVING RADIOISOTOPES
STABLE ISOTOPES
TARGETS
TOTAL CROSS SECTIONS