Extending the Kawai-Kerman-McVoy Statistical Theory of Nuclear Reactions to Intermediate Structure via Doorways

¹ Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6171, USA
² Texas A&M University - Commerce, P.O. Box 3011, Commerce, TX 75429, USA
³ Massachusetts Institute of Technology, 77 Massachusetts Ave., 6-306, Cambridge, MA 02139, USA
⁴ The University of Tennessee, Knoxville, TN, USA
⁵ Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
⁶ The University of Washington, Box 351560, 3910 15th Ave. NE, Seattle, WA 98195-1560, USA

^a e-mail: arbanasg@ornl.gov

Abstract

Kawai, Kerman, and McVoy have shown that a statistical treatment of many open channels that are coupled by direct reactions leads to modifications of the Hauser-Feshbach expression for energy-averaged cross section [Ann. of Phys. 75, 156 (1973)]. The energy averaging interval for this cross section is on the order of the width of single particle resonances, ≈ 1 MeV, revealing only a gross structure in the cross section. When the energy-averaging interval is decreased down to a width of a doorway state, ≈ 0.1 MeV, a so-called intermediate structure may be observed in cross sections. We extend the Kawai-Kerman-McVoy theory into the intermediate structure by leveraging a theory of doorway states developed by Feshbach, Kerman, and Lemmer [Ann. of Phys. 41, 230 (1967)]. As a by-product of the extension, an alternative derivation of the central result of the Kawai-Kerman-McVoy theory is suggested. We quantify the effect of the approximations used in derivation by performing numerical computations for a large set of compound nuclear states.