Measurements of the neutron transmission and capture cross sections inPb204

High resolution neutron transmission measurements have been performed on ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ in the energy interval $E=0.4-105\mathrm{}$ keV. The transmission data were analyzed using a multilevel $R$-matrix code to deduce resonance parameters. Previously obtained neutron capture data were reanalyzed in the interval 2.6-86 keV. Values of $\frac{G{\Gamma }_{\mathrm{n}}{\Gamma }_{\gamma }}{\Gamma }$ were determined from the capture data. For those resonances where ${\Gamma }_{\mathrm{n}}$ could be determined from the transmission data, the capture data were analyzed to extract ${\Gamma }_{\gamma }$. Our results yield an average capture for a stellar temperature $kT=30\mathrm{}$ keV of 89.5±4.5 mb. The $s$-wave level density for ${}_{}{}^{205}{}_{}{}^{}\mathrm{Pb}$ corresponding to the neutron energy range investigated (i.e., $E\sim 105$ keV) relative to that for ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ (which has about the same neutron separation energy) is greater by about a factor of 10. The average $s$-wave strength function in this energy region is determined as $S_0=0.93\mathrm{}\times {10}^{-4\mathrm{}}$. This is an order of magnitude greater than that for a similar energy region in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ + n where a doorway is observed at $E\sim 500$ keV. However, the strength function in the initial $E=0-100\mathrm{}$ keV in ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ + n is almost identical to the average value of that for ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ + n when the averaging interval for the latter is taken as $E_{\mathrm{n}}\approx 0-1000$ keV (i.e., over the doorway state). This suggests that the $s$-wave doorway state observed in the higher mass lead isotopes is completely mixed with "background" states in ${}_{}{}^{205}{}_{}{}^{}\mathrm{Pb}$, and most likely no intermediate structure will be observed in the $s$-wave strength function for the ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ + n reaction.