Nuclear Impulse in Electron Pair Creation

The nuclear impulses were studied for electron pairs produced in an air-filled cloud chamber by the continuous spectrum of x-rays from a 22-Mev betatron. Less than one-third of the momentum transfers to the nucleus were found to consist of values less than $\mathrm{mc}$. The probability $\Phi \left(P_n\right)$ of a momentum transfer $P_n$ was found to decrease rapidly with decreasing $P_n$ for $P_n<\mathrm{mc}$.