Photoneutron Cross Sections forV51andCo59

The ($\gamma , n$) and ($\gamma , 2n$) cross sections for ${\mathrm{Co}}^{59}$ and ${\mathrm{V}}^{51}$ have been measured, using 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 0.447±0.044 and 0.139±0.014 MeV-b for Co, and 0.451±0.045 and 0.106±0.011 MeV-b for V. The minus-second cross sections (${\sigma }_{-2\mathrm{}}$) are 1.82 and 1.56 mb/MeV, respectively, for these elements. The level density parameters $a$ were determined to be 5.49 and 6.18 Me${\mathrm{V}}^{-1\mathrm{}}$, respectively. The quadrupole moments determined from the compound-nucleus formation cross sections, $\sigma (\gamma , n)+\sigma (\gamma , 2n)+\sigma (\gamma , np)$, were found to be 0.94±0.13 and 0.66±0.09 b, respectively, for Co and V.