Bremsstrahlung Spectra Excited by the Beta Particles of ¹⁷⁰Tm

The external bremsstrahlung (EB) spectra generated in thick targets by the beta particles of ¹⁷⁰Tm are measured using a 4.55- × 5.08-cm NaI(Tl) crystal detector in a good geometry setup. The raw spectra are unfolded using the Liden-Starfelt procedure. The unfolded EB spectra are compared with Bethe-Heitler, Elwert-corrected Bethe-Heitler, Morgan-corrected Bethe-Heitler, and Tseng and Pratt theories. The experimental spectra are found to agree with the theory of Tseng and Pratt up to a certain energy and deviate positively thereafter. The deviation from theory increases with increasing energy and atomic number of the target material.