Momentum of Nucleons in Various Nuclei from the High-Energy Photoeffect

Abstract

The previously reported studies of the high-energy photoejection of neutrons and protons showed the basic validity of the "quasi-deuteron" model. Due to the motion of neutrons and protons in a complex nucleus one observes that the kinematics of the "quasi-deuteron" disintegration are modified from those of the photodisintegration of a free deuteron at rest. The modification of the kinematics was measured for Li, C, O, Al, and Cu in an attempt to compare the "average" momentum of the nucleons in these nuclei.It is found that a Fermi momentum distribution (with $T=0\ifmmode^\circ\else\textdegree\fi{}$) does not fit the observed data. A calculation employing only conservation of momentum and assuming a three-dimensional Gaussian momentum distribution for the neutrons and protons, gives an expression that fits the data quite well for Li, C, and O. The $\frac{1}{e}$ values of the Gaussians for Li, C, and O, respectively are 8, 19, and 19 Mev. These values have been corrected for the experimental angular resolution and for refraction at the nuclear surface.