Scattering of Protons by Hydrogen Near 18 Mev

Abstract

The differential cross section for the scattering of 18.2\ifmmode\pm\else\textpm\fi{}0.2-Mev protons by hydrogen has been measured over the angular range 30\ifmmode^\circ\else\textdegree\fi{}-90\ifmmode^\circ\else\textdegree\fi{} in the center-of-mass system. In order to reduce the over-all errors to less than 1 percent a 60-in. scattering chamber was used. Polyethylene, polystyrene, and nylon foils were used as scatterers while the proton-proton events were detected by observing coincidences between the scattered and recoil protons in anthracene photomultiplier counters. The incident proton beam was collimated to \ifmmode\pm\else\textpm\fi{}14 minutes of arc. Probable relative errors varied from 0.5 percent at 90\ifmmode^\circ\else\textdegree\fi{} to about 1 percent at 30\ifmmode^\circ\else\textdegree\fi{}, while the probable error in the absolute differential cross section at 90\ifmmode^\circ\else\textdegree\fi{} is estimated to be 1 percent. The data show a significant deviation from pure $S$-wave scattering and are best fitted by taking $S$-, $P$-, and $D$-wave phase shifts to be ${k}_{0}=54.1\ifmmode^\circ\else\textdegree\fi{}$, ${k}_{1}=+1.0\ifmmode^\circ\else\textdegree\fi{}$, ${k}_{2}=+0.4\ifmmode^\circ\else\textdegree\fi{}$, respectively.