Abstrakt
Thermal neutron radiative capture cross sections sigma(0 gamma) of Gd-155,Gd-157 are determined by summing the transition cross sections feeding the ground states of the respective product nuclei. The transition cross sections feeding the ground states from the discrete states in the low-excitation region, where the decay schemes are known completely, were measured using a guided cold neutron beam at the Budapest Research Reactor.
Transitions from the states at the higher excitation, the so-called quasi-continuum levels, are determined from simulations with the extreme statistical model normalized to the intensity balance through the low-lying discrete levels. A significant non-1/v correction was applied to Gd-155,Gd-157, leading to sigma(0 gamma)(Gd-155) = 56 700(2100) b and sigma(0 gamma)(Gd-157) = 239 000(6000) b.