Measurement of 75Se activity by correlation and coincidence counting

Development of multichannel time scaling technique to analyse the half-life of75mAs using correlation analysis

“…The results are consistent with the work of [17] and comparable with ones from [2,14,16]. Concerning the result of [5], the experimental method was consistent with the present study. However, they investigated the change of B(ε E β )f (λ, T ) in the rather limited regions where T 150 ms, so the value of B(ε E β ) was determined when χ 2 v (λ, B(ε E β )) approaches unity by successively changing both the uncorrelated parameters B(ε E β ) and λ.…”

“…In the following we shall briefly describe the formula available to determine the half-life of an isomeric state using a correlation counting experiment [5,6,11]. If the number of events n i in the ith time interval is recorded for N intervals of equal length T , then the variance V (ε E β , T ) and mean value n(ε E β , T ) are obtained from following formulae:…”

“…However, as pointed out in [2], since activities in this half-life range were invariably produced in addition to the desired one, difficulties were encountered in estimating the background. The correlation counting method is an alternative technique [3][4][5][6][7][8], based on the well known fact that decays of radionuclides follow Poisson statistics where the variance V of the distribution is equal to the mean value n, V = n. However, the principle is sometimes disturbed in cases such as 75 Se. This nuclide decays to 75 As by electron capture to several excited states of its daughter, as illustrated in figure 1 [9].…”

“…Therefore, one may observe two events for each decay populating the 304 keV state. In other words, this isomer plays a role of additional activity, so V = n [5,10,11]. According to the principle, the fraction (V − n)/n is related to a function f (λ, T ) (see section 2, equation ( 5)) which converges to unity for large λT .…”

“…According to the principle, the fraction (V − n)/n is related to a function f (λ, T ) (see section 2, equation ( 5)) which converges to unity for large λT . The correlation technique used in the determination of the half-life of the 304 keV state was reported by Smith et al [5]. They observed the variations of f (λ, T ) for up to T = 150 ms.…”