Determination of effective resonance energies for the (n,γ) reactions of 152Sm and 165Ho by using dual monitors

The effective resonance energies E¯r for the (n,γ) reactions of 152Sm and 165Ho isotopes were determined by using dual monitors (55Mn–98Mo) due to their favourable resonance properties. The samples were irradiated in an isotropic neutron field obtained from 241Am–Be neutron sources. The induced activities were measured with a high efficient, p-type Ge detector. The necessary correction factors for thermal neutron self-shielding (Gth), resonance neutron self-shielding (Gepi), self absorption (Fs) and true coincidence summing (Fcoi) effects for the measured γ-rays were taken into account. Thus, the experimental E¯r-values for above (n,γ) reactions are found to be 8.65 ± 1.80 eV for 152Sm and 12.90 ± 2.69 eV for 165Ho isotopes, respectively. The E¯r-values for both 152Sm and 165Ho isotopes were also theoretically calculated from the newest resonance data in the literature. Theoretically calculated E¯r-values are estimated to be 8.34 eV and 8.53 eV for 152Sm by two different approaches, which are generally, much smaller than that the present experimental value by 1.4–3.6% for 152Sm. In case of 165Ho isotope, the theoretically calculated E¯r-value of 8.63 eV from the first approach deviates substantially from the measured value by about 33%, whereas the theoretical E¯r-value of 12.95 eV from the second approach agrees very well with our experimentally determined E¯r-value. The results show that the present experimental E¯r-values for 152Sm and 165Ho isotopes agree with the calculated ones from the second approach within limits of the estimated uncertainty if the recently evaluated resonance data are used. However, it is worth noting that the results for E¯r-value calculated from the first approach are not satisfactorily accurate because of neglecting the neutron widths in that approach. Therefore, this study implies that it be regarded to the experimentally determined E¯r-value introduced in k0–NAA method for the determination of any analytical result rather than its theoretical value.