The Velocity of Gamma-Rays in Air

Abstract

The velocity of 0.5-Mev gamma-rays resulting from positron annihilation has been measured by means of scintillation counters and delayed-coincidence techniques. The value obtained is (2.983\ifmmode\pm\else\textpm\fi{}0.015)\ifmmode\times\else\texttimes\fi{}${10}^{10}$ centimeters per second.