Photoneutron Cross Sections ofTa181andHo165

The ($\gamma ,n$) and ($\gamma ,2n$) cross sections for ${\mathrm{Ta}}^{181}$ and ${\mathrm{Ho}}^{165}$ have been measured by use of nearly monochromatic photons obtained from the annihilation-in-flight of fast positrons. The integrated cross sections up to 28 MeV for $\sigma (\gamma ,n)$ and $\sigma (\gamma ,2n)$, respectively, are 1.32±0.13 and 0.93±0.09 MeV-b for Ta, and 1.47±0.15 and 0.90±0.09 MeV-b for Ho. Values obtained for ${\sigma }_{-2\mathrm{}}$ are 10.88 and 10.93 mb/MeV, respectively, for these elements. The level density parameters, $a$, were determined to be 15.7 and 22.0 reciprocal MeV, respectively. The intrinsic quadrupole moments determined from the compound nucleus formation cross sections, were found to be 6.71±0.74 and 7.40±0.90 b for Ta and Ho, respectively.