# Atlas of Neutron Resonances

*S.F. Mughabghab*

National Nuclear Data Center, Brookhaven National Laboratory

**Published by Elsevier Science, February 15, 2018**

**Preface:**

These two volumes form the sixth edition of what was
previously known as BNL-325,
Neutron Cross Sections, Volume 1, Resonance Parameters
(Third Edition, 1973) by S. F. Mughabghab and D. I. Garber.
The first edition of the BNL-325 reports which appeared in
1955 was prepared by Donald J. Hughes and John A. Harvey.
The fourth edition was published by Academic Press in
two parts in 1981 and 1984.
The fith edition was published by Elsevier in two volumes
on April 17, 2006. As with the last three editions, only
recommended parameters are presented. The present sixth
edition differs from previous editions in that available
capture, fission, and total neutron cross sections in the
keV-Mev neutron energy region were analyzed by the author
with the objective of determining average neutron resonance
parameters and compared to those obtained from the resolved
energy regions.
For more detailed information relating to experimental
data, the user is encouraged to consult the web site of the
National Nuclear Data Center at Brookhaven National
Laboratory,
*www.nndc.bnl.gov*.

In addition to the extensive list of detailed individual resonance parameters for each nucleus, this book contains thermal cross sections and average resonance parameters as well as a short survey of the physics of thermal and resonance neutrons with emphasis on evaluation methods. The introduction has been expanded to include commonly-used nuclear physics formulas and topics of interest such as direct or valence neutron capture, sub-threshold fission, the nuclear level density formula, and the treatment of electric dipole radiation in terms of the Fermi Liquid Model. As in the last edition, additional features have been included to appeal to a wider spectrum of users. These include (1) spin-dependent scattering lengths that are of interest to solid state as well as nuclear physicists and neutron evaluators, (2) Maxwellian average 30-keV capture cross sections that are of importance to astro-physicists, (3) s-, p-, and d-wave average radiative widths, gamma strength functions for s- and p-wave neutrons, and (4) nuclear level density parameters.

The various neutron strength functions are compared with optical model calculations and the radiative widths are calculated within the approach of the generalized Fermi Liquid Model and then compared with experimental data. Extensive application of the Porter-Thomas distribution, coupled with Bayesian analysis in the resonance region, was made in order to determine the parity of neutron resonances. The objective of achieving consistency between the thermal cross sections on one hand and the resonance parameters on the other is met by postulating negative energy resonances. Immediately preceding the resonance parameter tables, one can find the contributions to the thermal capture and fission cross sections from positive energy resonances for each spin state (for odd target nuclei) as well as the direct capture component calculated within the framework of the the Lane-Lynn approach. This information is required in nuclear structure investigations carried out with thermal neutrons and in the design of a thermal neutron polarizer.

The previous editions of BNL-325 have been widely used and extensively cited. We hope that this new edition will continue to be a prime resource which will satisfy the needs of the casual and serious users of neutron cross sections as well investigators interested in this rich field.