Nuclear Elastic Scattering of Photons near the Particle Threshold Energy (I)

The elastic scattering of photons near the particle threshold energy was studied for Al, Si, S, K, Ca, Ni, Cu, Cd, Sn, Pb and Bi. The bremsstrahlung x-rays from a 25 Mev betatron were used. The pulse of the primary x-rays was expanded up to about 30 µ sec to decrease the pile-up effect. The scattered photons were detected at the scattering angle of 120 degrees with the scintillation spectrometer using an 8''φ×8''NaI(T1) crystal and a 30 channel pulse height analyser gated the expansion signal of the betatron orbit. The energy at which the cross section has a peak was compared with the particle threshold energy and the value of cross section was compared with that of particle emission.