Electrodisintegration ofCu63,Zn64,Ag109, andTa181

The ratio of the ($\gamma , n$) photodisintegration cross section to the ($e, e^{\prime }n$) electrodisintegration cross section for the isotopes ${\mathrm{Cu}}^{63}$, ${\mathrm{Zn}}^{64}$, ${\mathrm{Ag}}^{109}$, and ${\mathrm{Ta}}^{181}$ was measured for electron energies of 24 to 35 Mev. This ratio was found to decrease with energy in contrast with the Weizsäcker-Williams approximation which predicts a constant ratio. However, the Weizsäcker-Williams method does yield a result which is of the right order of magnitude for Cu, Zn, and Ag and which is within a factor of two of the observed value of Ta.