Date of Award
Master of Arts
Masters Thesis-Open Access
The probability of annihilation of a positron with its antiparticle, an electron, is spin dependent. Since both particles have spin component one -half, there are two possible relative orientations of their spins they can either be aligned (parallel) in the 3S, triplet, state with total spin component │Sz│= ½ n - ½ n = 1 n or they can be opposite (antiparallel) in the 1S; singlet, state with│Sz│= ½ n - ½ n = 0. To conserve energy and angular momentum, annihilation from the triplet state must result in the creation of an odd number of photons -- predominately three. Similarly, annihilation from the singlet state must result in the creation of an even number of photons – predominately two.
Heavenrich, "A Direct Measurement of the Ratio of the Reaction Cross Sections for Two-Photon and Three-Photon Positron Annihilation in Aluminum and Silver" (1973). Master's Theses. 4278.