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 (1973) 156).
The energy averaging interval for this cross section is on the order of the width of single
particle resonances, 1MeV, 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. 42 (1967)
230). As a byproduct 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.
