Studies of internal bremsstrahlung spectrum of 35S beta emitter in the photon energy region of 1-100Â keV

The internal bremsstrahlung (IB) spectral photon distribution, produced by soft beta particles of 35S (Wmax=164 keV), in the photon energy region of 1-100 keV, is measured by using a Si(Li) detector, having high energy resolution and efficiency at low energy region. The measured spectral IB photon distribution is compared with KUB theory and Coulomb corrected IB theories given by Nilsson, and Lewis and Ford. After applying the necessary corrections, the experimental and theoretical IB spectral photon distributions are compared in terms of the number of IB photon of energy k per moc2 per unit photon yield. In the low energy region (below 10 keV), the experimental results are in agreement with all the theories. However, in photon energy region of 10-50 keV, experimental results are in agreement with Coulomb corrected Nilsson theory only, within the experimental errors. Further, beyond 50 keV, the Nilsson theory is more close to the experimental results than the KUB, and the Lewis and Ford theories. Hence, the Nilsson theory is more accurate than the other theories given by KUB and Lewis and Ford, particularly at a high energy end. The experimental results reported here with Si(Li) detector are free from number of ambiguities in earlier measurements reported with NaI(Tl) and HPGe detectors. The present results are indicating a relook into the theoretical considerations, given by different theories, while taking into account the Coulomb corrections for predicting the IB spectrum, particularly at high photon energy region.