The absolute differential cross section has been measured for 31.6-Mev protons scattered elastically from helium. Seven increments of angles from 15° to 51° in the laboratory system of coordinates have been measured simultaneously, using proportional counters.

The observed nuclear scattering is approximately three times the calculated Rutherford scattering for a scattering angle of 17° in the center-of-mass system and approximately 100 times the calculated Rutherford scattering for an angle of 62° in the center-of-mass system. Also, the differential cross section for a center-of-mass angle 55° has been observed to be 59.1 millibarns/steradian for incident protons of 19.5 Mev in the laboratory system.

• Received 25 August 1952

DOI:https://doi.org/10.1103/PhysRev.89.78