Electro- and Photodisintegration Cross Sections ofCu63

Highly monoergic electrons from a 22-Mev betatron have been used to study the ${\mathrm{Cu}}^{62}$ activity in a pair of 2-mil copper foils separated by a 10-mil copper radiator. The ratio of the photodisintegration to electro-disintegration in the foils decreases by less than 10% in the region from 14 to 20 Mev. The measured value of $F$ at 20 Mev is 8.6 in reasonable agreement with the extrapolation of previous measurements at higher energies and with the value of 8.38 expected on the basis of simple virtual photon calculations. Analysis of the excitation curves gave a ${\mathrm{Cu}}^{63}(\gamma , n)$ cross section of 80×${10}^{-27\mathrm{}}$ ${\mathrm{cm}}^2$ which is 20% below most previous measurements.