Threshold photoneutron spectra Page: 13 of 20
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c.
c.0 200 400
E (kWV)600 ,
Fig. 11. Comparison of radiation widths
and reduced neutron widths of resonances in
207Pb.l0 - zoPb(y, n) P=0.1 ~
-H
10
15{ I} and i resonances. The integrated M1 strength is not unusually large. However,
although about thirty z levels are expected between 0 and 300 keV, all the M1
strength for this group appears to be concentrated in resonances at 224 and 225 key.
Similarly, for - resonances below 600 keV, almost all the Ml strength is concen-
trated in the resonance at 606 keV. A statistical analysis indicates that the fre-
quency with which such a distribution can be generated by random fluctations is
< 10-3. Because the calculated difference between the filled fK orbital and the
f orbital -B MeV in this mass
1.o 0.5 region, the intermediate structure
iJ- could be interpreted in terms of a
0.5 two-quasi particle doorway consisting
- - - - - - of a iff ) (f) 1 particle-hole pair
o Y i h t' - o '57
0 100 200 300 0o o 200 300 coupled to the Fe ground state. A
4.0 spin-flip transition of an f' nucleon
- JZ would generate a particle-hole pair
2 57
2.0 which can couple to Fe to give rise
to doorways in both the ad
cc 200 300 400 500 600 700 channels. The sharpness of the
EnlkeVJ structure suggests that the damping
Fig. 12. Ground-state radiation widths widths of the doorway states are so
57
F 0 for resonances in Fe. small that the strength of each
doorway is spread over only a few
resonances.the particle-vibration doorway
interpretation of Beres and
Divadeenam in preference to the
view that there is a common
doorway.
Structure corresponding to a
simple doorway state has been
observed in the Ml excitation of
57
p-wave resonances in Fe. The
data are shown in Fig. 12. Spins
and parities were assigned from
angular distribution results and
comparisons with total neutron
cross section data for Fe. The
assignments indicate very sharp
concentrations of strength for both
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Jackson, H.E. Threshold photoneutron spectra, article, January 1, 1974; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1021993/m1/13/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.