THE YIELD FOR 2-PHOTON EMISSION FROM RADIATION OF THICK TARGETS BY A CD-109 CD-113M RADIOACTIVE SOURCE

Lehtihet and Quarles have reported the measurement of the two-photon yield from the radiation of thick targets of Ag, Au, and Pb by a Cd-109 radioactive source which has recently been found to have a significant component of Cd-113m. This means that there was a component of energetic electrons that was not considered in the original comparison of the data to a model calculation. Also, recent measurements of thick-target double bremsstrahlung produced by an electron beam have led to the development of a new, more rigorous model for the two-photon yield which can now be compared with the Cd-109-Cd-113m data. The Cd-113m component also produces a significant contribution to the coincidence yield from the coincidence of a single bremsstrahlung photon and a scattered electron. It is shown that the new model, with the single bremsstrahlung electron-photon coincidence contribution, provides a good description of the data.