A possible “doorway” state in 209Pb and 208Pb

Neutron Resonance Parameters of Bromine-79 and Bromine-81

“…(l3) examined level density systematics, and suggested level density multiplication factor of -11, when a doorway state splits into a family of fine structure states due to residual interactions. This factor may directly be observed to be 10-16 in the doorway states of 56Fe (14), 206Pb(15) and 207Pb(16), as the number of fine structures in these doorway states. In 81Br, the ratio of density of fine structure resonances to that of intermediate structures is about 70/5=14 below 15 keV, provided that small resonances (gr:<1.5 meV, observed mainly below 4 keV) are neglected.…”

Neutron Resonance Spectroscopy on 209Bi

“…In both 206Pb (Farrell et al 1965) and 207Pb (Newson 1972;Divadeenam et al 1973) the total integrated neutron strength below 1 MeV was found to be nearly equal to that found in the single doorway state in 208Pb + n. The plots of cumulative neutron strength versus neutron energy showed typical 'integral' -shaped behaviour, which indicated a considerable increase in the· spreading width of the doorway state the further one moved away from the closed shell configuration. A preliminary analysis of poorly resolved data (obtained by F. T. Seibert and others), extending to ~600 keY bombarding energy in 209Bi+n, has never been published, although a plot of the cumulative neutron strength versus neutron energy based on these data was presented by Divadeenam et at.…”

Decay ofNb94andNb94m

“…9 Figure 1 is a drawing of the apparatus built to do this job. The neutron source is the 7 Li(p } n) 7 Be reaction pro- Measurements are reported on differential elastic scattering of neutrons of a few keV energy spread from 99.75% 208 Pb in the energy region 0.715 to 1.761 MeV. The results include absolute differential cross sections at 20 resonant and 9 nonresonant energies.…”

“…The source of the 2X10 4 -yr Nb 94 was produced by neutron irradiation of spectroscopically pure niobium metal powder. 7 Approximately 1 mg of the Nb 94 , in the form of niobium metal, was dissolved in a solution of HF and HNOs, which, with the addition 6 of H 2 0, glycerin, and SnCl 2 , brought the total weight to approximately 20 mg. Only 1.1 mg of this solution was used to form the scintillator sandwich described earlier and the counting rate obtained from the Nb 94 beta activity was low enough to avoid possible difficulties with accidental coincidences from either the Nb 94 activity or with x rays from 12-yr Nb 93m present as a contaminant.…”

“…To produce the 6.6-min Nb 94m activity, 5-mg samples of "Specpure" Nb metal were irradiated for periods of several minutes in a neutron flux of 4.5 X10 12 w/cm 2 7 For details of the source preparation and purification, see sec at the University of Michigan Ford Reactor. The singles spectrum was taken using a xenon-filled proportional counter, and the data were recorded with a multichannel analyzer.…”