The Annihilation of Fast Positrons by Electrons in the K-Shell

摘要: The probability of the simultaneous a positron and an electron, with emission two quanta radiation, has been calculated by Dirac several other authors. From considerations energy momentum it follows that electron can only annihilate one another quantum radiation in presence third body. An bound atom could, therefore, positron, represented hole on theory, jumping into state negative which happens to be free, nucleus taking up extra momentum. process is now mathematically analogous photoelectric transitions states sense matrix elements concerned are same, we might expect effect would most important for electrons K-shell. Fermi Uhlenbeck have approximately, condition where kinetic order magnitude ionization result they obtained was very small compared process, explained fact these energies, does not get near nucleus. In view positrons energies 100 mc 2 occur considerable quantities showers produced cosmic primary itself may consist, part, positrons, becomes interest calculate cross-section annihilation high K-shell, their absorption matter, also compare this energies. hard γ -rays, leaves different angular (described azimuthal number l ), terms give largest contribution roughly those -ray 2. For calculation method Hulme, last step carried out numerically, question, must find some approximate effecting summation. We shall use adaptation Sauter's method, treat as product fine structure constant nuclear charge. This expected good approximation Our further restriction valid when