External bremsstrahlung spectra excited by 32P and 35S beta rays in different elements

The spectra shapes of the external bremsstrahlung produced by 32P and 35S beta rays when they are completely absorbed in different elements such as carbon, aluminium, copper, silver, tin and lead are experimentally measured with a multichannel NaI(Tl) scintillation spectrometer along with a standard geometrical arrangement. After making all the necessary corrections, the final distributions are compared with the modified Bethe-Heitler theory. The experimental results are in excess over theory for high Z elements and this experimental excess over theory is found to increase with increasing nuclear mass and photon energy.