Thermal Neutron Capture Cross Sections Of Isotopes PDF Download

We have measured precise thermal neutron capture {gamma}-ray cross sections {sigma}{sub {gamma}} for all stable Palladium isotopes with the guided thermal neutron beam from the Budapest Reactor. The data were compared with other data from the literature and have been evaluated into the Evaluated Gamma-ray Activation File (EGAF)[1]. Total radiative neutron capture cross-sections {sigma}{sub 0} can be deduced from the sum of transition cross sections feeding the ground state of each isotope if the decay scheme is complete. The Palladium isotope decay schemes are incomplete, although transitions deexciting low-lying levels are known for each isotope. We have performed Monte Carlo simulations of the Palladium thermal neutron capture de-excitation schemes using the computer code DICEBOX [2]. This program generates a level scheme where levels below a critical energy E{sub crit} are taken from experiment, and those above E{sub crit} are calculated by a random discretization of an a priori known level density formula {rho}(E, J{sup {pi}}). Level de-excitation branching intensities are taken from experiment for levels below E{sub crit} and the capture state, or calculated for levels above E{sub crit} assuming an a priori photon strength function and applying allowed selection rules and a Porter-Thomas distribution of widths. The calculated feeding to levels below E{sub crit} can then be normalized to the measured cross section deexciting those levels to determine the total radiative neutron cross-section {sigma}{sub 0}. In this paper we have measured {sigma}{sub 0}[{sup 102}Pd(n, {gamma})] = 0.9 {+-} 0.3 b, {sigma}{sub 0}[{sup 104}Pd(n, {gamma})] = 0.61 {+-} 0.11 b, {sigma}{sub 0}[{sup 105}Pd(n, {gamma})] = 21.1 {+-} 1.5 b, {sigma}{sub 0}[{sup 106}Pd(n, {gamma})] = 0.36 {+-} 0.05 b, {sigma}{sub 0}[{sup 108}Pd(n, {gamma})(0)] = 7.6 {+-} 0.6 b, {sigma}{sub 0}[{sup 108}Pd(n, {gamma})(189)] = 0.185 {+-} 0.011 b, and {sigma}{sub 0}[{sup 110}Pd(n, {gamma})] = 0.10 {+-} 0.03 b. We have also determined from our statistical calculations that the neutron capture state in {sup 107}Pd is best described as 2{sup +}(60%)+3{sup +}(40%). Agreement with literature values was excellent in most cases. We found significant discrepancies between our results for {sup 102}Pd and {sup 110}Pd and earlier values that could be resolved by re-evaluation of the earlier results.